Juan Mata has warned Chelsea of the dangers of Basle and complacency as the Blues bid to reach a European final for a second successive season.
David Luiz's stoppage-time free-kick in Switzerland last week earned Chelsea, last season's Champions League winners, a 2-1 first-leg advantage in their Europa League semi-final with the Swiss champions ahead of Thursday's return clash at Stamford Bridge.
``It's going to be a dangerous game,'' Mata said.
``Even though we have two goals away, a great result, it's that kind of game that can be very risky.
``If we don't go into the game thinking about winning, thinking about defending well, thinking about trying to win again, it's going to be difficult.
``We still know we have to fight if we're going to be in the final.
``We got a great result in Switzerland, but now we have to play another 90 minutes and I'm sure they're not going to give up.
``They're a team who try until the end. It will be tough, for sure.''
Basle have recorded numerous upsets en route to their first European semi-final, advancing at the expense of Zenit St Petersburg and Tottenham, and have proven their ability to surprise.
The winners will face either Fenerbahce or Benfica in the May 15 final in Amsterdam and Chelsea interim boss Rafael Benitez is taking nothing for granted despite his side's commanding position.
``We have an opportunity, but my concern is we'll be thinking we're in the final - it's not the case,'' Benitez said.
``We'll play against a very good team, a team that has scored goals away, so everybody has to realise it will be tough, it will be difficult.
``I think they will come trying to score. They did it against Tottenham.
``I'm sure they will be offensive, they will push. They will try to score because it's the only way for them to qualify.
``I am concerned, but I'm not afraid. We know it's a dangerous team.
``We're so close to the final we have to be really focused, concentrated and not make mistakes. I have a lot of confidence in my players.''
Benitez does not intend to think too far ahead, meaning Luiz is among those who could play despite the fact if he receives a yellow card he would be suspended and miss the final.
Ashley Cole is banned, while his fellow left-back Ryan Bertrand and midfielders John Obi Mikel and Ramires, who came off midway through the first half of Sunday's win over Swansea with a dead leg, are also on yellow cards.
Frank Lampard, who requires one goal to equal Bobby Tambling's club goalscoring record of 202, is in line to start, as is John Terry.
If the captain does play, it will be his third successive start for the first time in 2013.
Basle are confident of pulling off a minor miracle and winning at the home of last season's Champions League winners.
The Swiss champions have never won a match in England and Basle boss Murat Yakin said: ``Every game is difficult and we know we're playing against Chelsea, who are the Champions League winners. They have two top players in every position.
``But we will do everything. We will be brave, we'll play with confidence and who knows? Maybe we can achieve a small wonder and we can qualify for the final.''
Forward Valentin Stocker added: ``It will be important if we can actually take the lead. If we have that confidence that we can score a goal here, maybe that can psychologically affect the whole team and maybe in that way we can achieve a small miracle.''
Despite their impressive run to a first European semi-final - a streak which has included wins over Zenit St Petersburg and Tottenham - Basle are still to win away from home in the tournament.
Chelsea, meanwhile, are unbeaten in 12 European ties at Stamford Bridge, their last defeat coming to Manchester United in the 2010/11 Champions League quarter-finals.
``I don't hold much for statistics,'' Yakin said.
``What I want is that we play here, we play very good football and that we start well.
``Chelsea are defensively very good, they are very good in attack, but our team also has very good qualities.
``We have shown that against Tottenham, what we're capable of doing.
``We're very happy to be here. We will be trying everything to get to the final. We will fight hard, we will give passion. We know it's difficult - we've got a 2-1 deficit to catch up.
``We will do our best here.``