Manchester City boss Roberto Mancini knows Adam Johnson can make life difficult for his side as he returns to the Etihad Stadium this weekend.
Mancini often tipped Johnson for big things after signing him for £7million in 2010 but the winger grew frustrated at a lack of first-team opportunities and joined Sunderland in August.
The 25-year-old spoke of his frustration and of difficulties with Mancini after making the £10million move from the Barclays Premier League champions back to his native north east.
The England international will now get the chance to show City what they have lost as the Wearsiders visit Eastlands for a Saturday lunchtime fixture.
Mancini said: ``I think Adam played well here. The problem was maybe that he didn't play always. For young players like him it is important to play every game.
``I am sure he will do well for Sunderland and go to another top team because he deserves this. He is a good guy and a good player.
``I hope he can have a good game on Saturday because I like Adam, I think he is a really good player.
``He wanted to play every game and here it was difficult, he decided to leave.''
City were well aware of the problems Sunderland can pose even before they signed Johnson.
Last season the Black Cats did more than any other side to derail City's title bid, beating them at the Stadium of Light and then claiming a draw at Eastlands.
They were in fact only five minutes from winning that second game as well, but two late goals saw the hosts snatch a point in a 3-3 thriller in March.
Mancini said: ``It is very difficult because every time Sunderland play against us they play a fantastic game.
``Last year the point we got against Sunderland after we were 3-1 down with five minutes to go, and we equalised in the end with (Aleksandar) Kolarov, was an important point in the league.
``I think we need to remember that game. It is important we get three points but it will be a tough game. We need to play well.''
John O'Shea has warned his Sunderland team-mates last season's heroics against City will count for nothing this time around.
Sunderland were the only side to deny Mancini's men Premier League victory on their own pitch as they clinched the title, although O'Shea, who was missing through injury that day, knows recent history will have no bearing at all when they return on Saturday.
The former Manchester United defender, who helped his side to a first league win of the season against Wigan last weekend, said: ``It's a totally different situation. City have added to their squad, we have added to our squad and made some changes along the way.
``Hopefully Adam Johnson will be able to give us a bit of inside info and we can see how Mr Mancini works.
``But look, it's a tough game for us, we are under no illusions. We will have to play very well.
``But it's one we can go into now with confidence because we got that win against Wigan, and have had all the good performances away from home.
``It's been put to bed, we have got that win on the board and we can move forward now.``