Liverpool manager Rafa Benitez went back into hospital on Wednesday for a third operation on kidney stones, leaving assistant Sammy Lee in charge of the Premier League leaders.
Lee said he hoped the Spaniard would be out in time for next week's two matches against Merseyside rivals Everton.
"It's a difficult time for him because you know Rafa Benitez, all he wants to do is be out there on the training pitch with his players," Lee told the club's website.
"He's going for the third operation but we're hoping it won't keep him out for too long, hopefully just a couple of days."
Liverpool host Everton in the league on Monday before the teams return to Anfield for their FA Cup fourth-round tie on Sunday week.
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