Fernando Torres has expressed his disappointment at being unable to face former side Atletico Madrid in this week's Europa League semi-final.
Torres had surgery in Barcelona on Sunday night to repair damaged cartilage in his right knee, a problem that resurfaced after a similar operation in January.
He told his official website: "I really wanted to play against Atletico. I wanted to come back and say hello to people because for me this tie is special."
Torres would liked to have travelled with his team-mates to Madrid this week but is focused on his recovery. He said: "I cannot do it for the recovery process. Every day counts now."
Due to the ash cloud over Europe, Torres only just made it to Barcelona in time for the operation. He said: "On Saturday they cancelled the flight and in half an hour we had to organise the trip. It was very difficult, but luckily we got a ticket to cross the Channel Tunnel. The trip was an adventure.
"I arrived in Barcelona at 8.30pm on Sunday, with barely time to shower in the hotel and go to the clinic where I met Dr. Cugat. Three hours later I had the operation."
Torres is due to be sidelined for up to six weeks, making him a major doubt for the World Cup, but Torres remains confident that he will be fit.
He said: "The World Cup is more important now. The timing of the injury has been complicated and the penalty is not to have played more games and scored more goals. I have waited four years and I do not plan to miss out. Today I'm starting to work."