Liverpool boss Rafael Benitez revealed that Gerrard has been playing through constant pain after the Anfield side forced their way into the Champions League group stages.

Benitez said: "He has a groin problem so he will have an operation and could be out for 10 to 15 days. It is not serious but we need to do it now."

A goal two minutes from the end of extra-time by Dirk Kuyt gave Liverpool a 1-0 aggregate victory over a brave Standard Liege side in the third qualifying round.

But it was clear that Gerrard was not at his best, and he was due to go under the knife on Thursday to make sure he is fit to lead Liverpool into the group stages in September.

Gerrard will miss Liverpool's trip to Aston Villa on Sunday, the England games with Andorra and Croatia and possibly the Reds' home league game with Manchester United on September 13.

"He has been playing some games in pain, not being 100% fit and we decided that this was the best moment for the operation," Benitez added.

"He had a problem for the first game with Liege, and also when he went away to play for England in their friendly last week against the Czech Republic.

"We talked with the doctor yesterday and today, and it was decided that Steven would play in this match with the pain. But now we will have to get the situation solved."

Gerrard produced a match-winning late goal on Saturday against Middlesbrough, but despite a determined display against Liege, he was clearly carrying an injury in the 30 minutes of extra-time.

Liverpool, despite another worrying display, are now in the group stages draw on Thursday in Monaco.