It is one of football management's most time-honoured idioms. Once you are done at a club, do not return for fear of diminishing returns. Some of the biggest names in the game have tried but very few have overturned it. Jose Mourinho is the latest to attempt to do so.
Udo Lattek (Bayern Munich, 1970-75 and 1983-87)
Despite lacking experience in top-level management, Lattek had arrived in Munich in 1970 on the recommendation of Bayern star Franz Beckenbauer, who had been impressed by his efforts as assistant coach with the West German national team. The appointment proved highly successful, with Lattek securing the DFB-Pokal and three league titles as well as the 1974 European Cup, but he exited in January 1975 after a spell of poor form.
He was swiftly employed by Borussia Monchengladbach, and won league titles in 1976 and 1977 as well as the 1979 UEFA Cup. In 1982, he won the Cup Winners' Cup with Barcelona, but he left the Camp Nou the following season amid disappointing results and reports of rifts behind the scenes.
Bayern general manager Uli Hoeness, seeking a replacement for Pal Csernai after a disappointing campaign, then brought his former coach back and it proved highly successful: Lattek won the Bundesliga title three times in succession, the DFB-Pokal twice and reached the 1987 European Cup final.
Valeriy Lobanovsky (Dynamo Kiev, 1974-90 and 1997-2002)
A legendary coach with Dynamo Kiev in his first spell, Lobanovsky became the first manager of a Soviet side to win a major European trophy, securing the Cup Winners' Cup in 1975 and 1986, along with eight league titles.
During his time with Kiev, he also had three spells in charge of Soviet Union, and led the team to the final of the European Championship in 1988 but, with the USSR falling apart, he opted to leave the country after the 1990 World Cup and headed off to the United Arab Emirates.
In 1997, he made his return to Kiev, securing five straight league titles and, perhaps more impressively, taking a team featuring the talents of Andriy Shevchenko and Sergei Rebrov to the Champions League semi-finals in 1999. His second reign suffered a sad end: Lobanovsky died in 2002 following a stroke.
Giovanni Trapattoni (Juventus, 1976-86 and 1991-94; Bayern Munich, 1994-95 and 1996-98)
After a brief spell with Milan, Trapattoni proved hugely successful during a decade-long spell with Juventus in which he won six league titles, two Coppa Italia, the European Cup, the UEFA Cup and the Cup Winners' Cup.
However, in March 1986 it was announced that he would join Inter at the end of the season. He said he had been thinking about moving on for the last five years, and had turned down an offer from Real Madrid because he wanted to stay in Italy, so joined arch-rivals Inter.
He would spend five years with Inter, winning one Serie A title, and signed off with the 1991 UEFA Cup; Juve negotiated his return that summer, and he spent a further three years in Turin, during which he secured the 1993 UEFA Cup.
Trappatoni, who had told Der Spiegel in 1991 that he hugely admired the German winning mentality, later had two spells in charge of Bayern, who have made a habit of re-employing coaches. The first stint, which lasted a single season, saw Bayern finish sixth during a year in which he blundered by fielding too many amateur players.
He then returned to Italy with Cagliari but was back in Munich a year later, and secured the Bundesliga in his first season and the DFB-Pokal in his second. His German adventure ended there, though, as the famous disciplinarian found himself unable to control the stars of "FC Hollywood".
Howard Kendall (Everton, 1981-1987, 1990-1993 and 1997-98)
Third-time lucky certainly did not apply to Kendall, whose final spell at Everton ended in the narrowest of escapes from relegation. The club he had taken to the very edge of greatness was no longer the same. Time had caught up with him and his hairline.
Kendall is one of Everton's greatest players too, and he was just 35 when he took over a club shrouded in the shadow of its neighbour in red. He came very close to the sack before an FA Cup win in 1984, and a title the following year made Everton the best club in the land. Despite losing a double to Liverpool in 1986, the following year saw the reclamation of the old Football League title. However, the Heysel riot of 1985 had stopped Everton playing in the European Cup, and a frustrated Kendall left in the summer of 1987 for Athletic Bilbao.
With Everton struggling under former assistant Colin Harvey in 1991, Kendall gave up a good thing at Manchester City, but the magic was gone - the club had never recovered from its exile and his departure. He left in December 1993, only to return in the summer of 1997. By then, he was just as out of ideas as his club clearly was in its choice of managers.
Jupp Heynckes (Bayern Munich, 1987-1991, 2009 and 2011-13)
Having taken over a Bayern Munich in mourning after the loss of the 1987 European Cup final, Heynckes went on to win two Bundesliga titles before getting the sack after a poor start to the 1991-92 season.
His recently concluded treble at Bayern was actually a case of third time lucky, since he was the caretaker manager that guided "FC Hollywood" into the Champions League after Jurgen Klinsmann's disastrous spell in charge. He replaced Louis van Gaal in the summer of 2011 and, despite losing the 2012 Champions League final, won it the next year, his team winning the Bundesliga by a ludicrous margin.
Heynckes has just ruled himself out of his third return to a former club: having already managed Borussia Monchengladbach twice, he said on Tuesday he would not be going back to Real Madrid, with whom he won the Champions League in 1998, before promptly being sacked.
Kenny Dalglish (Liverpool, 1985-1991 and 2011-12)
The magic deserted Dalglish on his return to the place where he is worshipped. His defenders, and they are legion, will point to the winning of a League Cup and a losing visit to the FA Cup final, but King Kenny's return ended in a rancorous failure to return to the Champions League.
Having lifted the club from the desperately tragic lows of Heysel and Hillsborough, Dalglish bowed to the pressure in February 1991 with three titles and two FA Cups to his name. Heysel meant his Liverpool team never got the chance to play European football.
When a tracksuited Dalglish followed out his team in January 2011, after stepping in following the removal of Roy Hodgson, there was a glimpse of a glittering yesteryear. At first, Dalglish looked glad to be back, wisecracking away with the press. But once his job was made permanent, the pressure began to tell. A disastrous summer transfer window was followed by horrible handling of the Suarez-Evra affair. The shutters went down, the smile was completely gone and, eventually, so was Dalglish.
Fabio Capello (AC Milan, 1991-96 and 1997-98; Real Madrid 1996-97 and 2006-07)
The English press need not fear his return to FA HQ, but Don Fabio has never had a problem with returning to the scenes of his successes, even if one of his grand returns was something of a disaster.
His second spell with AC Milan in 1997 was a pallid imitation of his all-conquering previous spell at San Siro. The first time, he had succeeded Arrigo Sacchi and dominated Serie A in a fashion his predecessor never could, going unbeaten for 58 games between May 1991 and March 1992 and then winning the Champions League in 1994 by pummelling Barcelona 4-0 in Athens.
The second spell saw Capello's team finish tenth, and this represented the only time he failed to manage a club team to a league title. Who had he replaced? Sacchi, who had similarly failed to recreate the old magic when he returned to Milan in the middle of the 1996-97 season.
During Sacchi's struggle at Milan came Capello's first season at Real Madrid, which ended in a Liga crown, but he agreed to leave in April as a result of Madrileno dissatisfaction with style of play as well as a fall-out with Raul, the young king of the Bernabeu, and the club's president. A decade later, Capello came back to repeat the trick, this time falling out with David Beckham and Ronaldo, but still won the title before being removed once more.
Kevin Keegan (Newcastle United, 1992-1997 and 2008)
Few Messiahs get the chance to make two returns, but King Kev got just that. As a player, he had made Newcastle the final stop in a glittering playing career, and got the Magpies back into the First Division.
His 1992 mission, once he accepted it, was keeping them in the Second Division after years of neglect had the club spiralling downwards. Keegan served as a one-man PR machine for the Geordie nation as he led them into the Premier League, inspiring a brand of football where the foot was never taken from the accelerator, defence rarely factored in.
Thus, the title was blown at the end of 1995-96 but the fans still loved him, and were devastated when he walked away in January 1997, having already decided to quit at the end of the season. As the club struggled, Keegan remained the popular choice to return. The club's owner, Mike Ashley, gave the fans their wish in 2008, but soon shifted the goalposts for the living legend. After a fine start to the 2008-09 season, Keegan walked once more, but would later win a tribunal case to prove he had been undermined.
Marcello Lippi (Juventus, 1994-99 and 2001-04; Italy 2004-06 and 2008-10)
"He's a handsome bastard" was Sir Alex Ferguson's description of his friend and frequent adversary. Handsome bastards often get invited back, and Lippi has twice returned to the scenes of his successes, though with hugely mixed results.
The Bianconeri's return to the top table of European football was masterminded by the be-spectacled coach. He won three Scudetto and the Champions League in 1996, with his team losing in the finals of 1997 and 1998 too. Juve were a machine that stopped working properly once he was tempted to Internazionale. He returned to Turin to repeat his domestic success with two titles in 2002 and 2003, and yet another Champions League final loss in the latter, this time on penalties.
Italy could not have employed a more qualified coach and were rewarded in 2006 with the World Cup. Lippi departed a champion but was tempted back after Roberto Donadoni's team flopped at Euro 2008. Italy were terrible at South Africa 2010, losing the final group game to Slovakia in Johannesburg, and exiting as last in their group, behind New Zealand.
"If a team turns up with terror in their heart and legs, and is unable to express its ability, it's because the coach didn't train them as he should," he admitted at Ellis Park.
Louis van Gaal (Barcelona 1997-2000 and 2002-03; Netherlands 2000-02 and 2012-present)
Another serial returner is Aloysius Paulus Maria van Gaal, King Louis to you, never knowingly short of self-confidence. Having conquered Europe with Ajax, he was the hottest property in European coaching, his ideas copied across the continent. Barcelona just had to have him, dispensing with Sir Bobby Robson, despite his winning the Cup Winners' Cup the previous season.
Van Gaal attempted to recreate Amsterdam in Catalunya, and won two titles, but never quite managed to get his message across, least of all with the local media, who never took to his brusque manner. The Dutch tradition of achieving success in spite of fall-outs did not work out, and he left congratulating the press on forcing him out.
Two years later, he was back at the Camp Nou, after former right-hand men Llorenc Serra Ferrer and Carles Rexach flopped too, but lasted just four months of the 2002-03 season before Frank Rijkaard began the Barca we know today. In between, he had failed to qualify the Netherlands for the 2002 World Cup, a role he is now undertaking once more. He even once returned to Ajax too, a short-lived and typically stormy spell in 2004 as technical director.
Ottmar Hitzfeld (Bayern Munich, 1998-2004 and 2007-08)
A year after securing the Champions League title with Borussia Dortmund, Hitzfeld headed off to Bayern, and was an instant success. His new side finished 15 points clear at the top of the Bundesliga in his debut season, reached the DFB-Pokal final, and were defeated in the Champions League only by virtue of Manchester United's dramatic injury-time comeback.
The Bundesliga title was secured in four of his six seasons, and he won the DFB-Pokal twice, while in 2001 he led the club to Champions League glory as they defeated Valencia on penalties. He was Bayern's most successful coach of all time but, after a disappointing 2003-04 campaign, his position came under scrutiny. He stated his intention to remain until his contract expired in 2005 but was relieved of his duties that summer, with Uli Hoeness, the club's general manager, saying a change was necessary as the players were "all too spoiled".
Arch-disciplinarian Felix Magath was brought in, securing back-to-back domestic doubles in his first two campaigns, but his third was disappointing and he was fired in January 2007 with the club in fourth place. Hitzfeld - in self-imposed exile from football - accepted the offer to return, but was unable to achieve his stated aim of guiding the club into the Champions League places.
That summer, Bayern spent heavily, bringing in the likes of Franck Ribery, Miroslav Klose, Luca Toni and Ze Roberto. The spending paid off as Bayern secured the Ligapokal, DFB-Pokal and Bundesliga but Hitzfeld rejected the offer of a new contract. The coach - previously a maths teacher - had been offended when advised by the club's chief executive, Karl-Heinz Rummenigge, that "football is not mathematics" after a 2-2 draw against Bolton in November 2007. "At that time I was still considering extending my contract," he said.
Hitzfeld opted to take charge of Switzerland at the end of the season.