Manuel Almunia admits Arsenal will be a weaker side without talismanic skipper Cesc Fabregas.
The Spanish playmaker picked up a hamstring injury in the 3-1 victory over Burnley on Saturday and will sit out Tuesday's crucial UEFA Champions League with Porto as a result.
In Fabregas' absence, the captain's armband is set to pass to experienced shot-stopper Almunia.
He is honoured to be handed such responsibility, but admits he would rather have been following Fabregas out of the tunnel.
"Cesc is the spirit of this team - he is our captain, he is a fantastic player and every time he is not on the pitch we miss him a lot," said the Gunners keeper.
"But all the players are convinced and 100 per cent committed to get through."
Arsenal trail 2-1 heading into the Emirates Stadium showdown, with costly errors having cost them dear during the first leg in Portugal.
Arsene Wenger's men know they need goals and will be looking to their frontmen to provide the ammunition.
Danish striker Nicklas Bendtner endured an afternoon to forget against Burnley at the weekend, spurning a host of glorious opportunities, but Almunia has backed the youngster to make amends in Europe.
"Nick is a special guy. He is young and he is learning," he said.
"I think he needs people around him who tell him the truth all the time.
"When he does well, of course everybody will tell him he is good - but when he misses goals he needs someone to push him to improve. That is what we try."
Almunia added: "I hope he reacts tomorrow and I think he is encouraged by the chances he missed in the game against Burnley. He has been training very well."