Rafael Benitez admits he does not know when John Terry will be fit to return to the Chelsea team, but insists he was delighted with his side's "amazing" performance in the Capital One Cup on Thursday evening.
Terry watched the Blues' 5-1 quarter-final win over Leeds from the substitutes' bench, having travelled to Yorkshire. But he was not in Chelsea's matchday squad and Benitez said that the knee injury which has sidelined Terry since November 11's 1-1 draw with Liverpool, when he scored and was then hurt, remains a concern.
"Still I say we don't know," Benitez said. "One day he is fine, the day after he has some pain."
Terry has sat out the last 10 games and could be in contention to face Aston Villa on Sunday but Benitez has not set a date for the central defender's comeback.
"With the knee it is always very difficult to say," he added. "We don't know if it will be one day or one week."
Chelsea's victory took them into the semi-finals where they will face Swansea and Benitez said: "When you go to a semi-final, any team is difficult. Swansea is a good team, they are playing well. They like to play football, on the floor and it will be interesting."
Benitez praised his players for their character at Elland Road, as they scored five second-half goals after trailing to Luciano Becchio's 37th-minute shot.
"We were looking for character and the reaction was so good, we have to consider it for the future. The reaction in the second half was fantastic, especially with travelling back from Japan and having jet lag.
"The second half was amazing. Coming back we needed to see the fitness of the players and we had to decide to change some of them, so to have this reaction, being mentally ready and after working so hard and playing so well, I'm really pleased with them."
After losing the World Club Cup final, Chelsea's win puts them on course for a first trophy of Benitez's reign and he said: "Every competition is important for us and a top side like us has to win every competition."