Boss Glenn Hoddle explained that he had hoped the striker would be able to undergo a fitness test ahead of the game, but he still had a high temperature.
"Sergei has had two days in bed with bad flu," said Glenn after the victory. "We tried to get him out for a fitness test today, but he wasn't even well enough to get out of bed. He's had a temperature for two days."
The assembled press corps once again questioned the boss on Sergei's future at the club.
"Everyone keeps asking me the same question about Sergei. The lad has scored 24 Champions League goals and is a talented player.
"At the moment he's not firing on all cylinders, but that's a challenge for him, for me and for everyone at the club. We can get that extra per cent out him next season.
"Any club now, if offers come in for players and Liverpool are no different, they are going to look at it because of the financial constraints on clubs - it's changing."
Sergei Rebrov was in bed suffering from flu while the team turned on the style against Liverpool on Saturday.