Porto goalkeeper Iker Casillas has warned that Chelsea can still beat any of their European rivals, despite their poor start to the season, ahead of the Portuguese club's trip to Stamford Bridge in the Champions League on Wednesday night.

Porto are second in Group G, behind leaders Chelsea only on goal difference, ahead of the final group stage round of fixtures this week and both teams know that victory would secure their place in the last 16.

Casillas, who had a notably fraught relationship with Blues manager Jose Mourinho during his time in charge of the goalkeeper's former club Real Madrid, knows that his old boss will be gunning for victory against the club he led to the Champions League title in 2004.

The 34-year-old told the Sunday People: "Mourinho is a coach who will always want a victory and now against his old club, but we fly with the mentality that we can make them suffer at Stamford Bridge and get through the group phase.

"To be out of the Champions League in the next few days would be a big blow. Chelsea are not playing with the same level that they played in the past seasons but the Blues have an enormous squad that is capable of beating any European rival.

"It is never easy to play English clubs in their own stadiums with the atmospheres there, but this match is decisive for us. After failing in the last match it is now obligatory that we go to London and show our best side and, as a minimum, take one point on the pitch."

A draw would take both sides through if Dynamo Kiev fail to beat Maccabi Tel Aviv in the other Group G game.