Deco limped off shortly before halftime and manager Guus Hiddinks was pessimistic about his chances of recovering to play much of a role in the remainder of Chelsea's campaign.
"He was fit, he worked hard the last weeks and played his games," Hiddink told Chelsea's website.
"After 20 or 25 minutes he got his problem again and I think he will be out for a while."
"That's a pity, I think when he starts now he has to be very long and intense after his recovery medically to be very fit, so I have my doubts to be honest (about the rest of the season) but let's see in the upcoming time."
There was better news regarding striker Didier Drogba who also failed to finish the game and the form of fit-again midfield dynamo Michael Essien who scored the winner in the 1-0 victory which moved Chelsea back into second place, four points behind Manchester United.
"Drogba I think is not a big problem," Hiddink said. "He likes to be with the team, he likes to train, he likes to play so I think he will be recovered very soon. I think tomorrow or the day after he will be OK."
Hiddink said Essien's return to fitness from a cruciate knee ligament injury that had sidelined him since August was a huge boost with an FA Cup semi-final and a Champions League quarter-final on the horizon.
"For the team and the crowd I think it's very important that he came back after a long period of recovery," said Hiddink. "I knew him before and he is very strong and gives a lot to the team."
Hiddink said United were still firmly in the driving seat to win an 18th league title despite their 4-1 hammering by Liverpool at Old Trafford on Saturday.
"Let's see how they react in the upcoming days but it's not the first time it has happened and the big teams always react," he said. "If we want to track them then we have to keep winning which we are doing."
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