Manchester United captain Nemanja Vidic has been ruled out for two months after undergoing knee surgery, the club confirmed.

Vidic only just returned from a six-month layoff after rupturing his cruciate in last season's Champions League game against Basel. The influential defender missed Sunday's game against Liverpool after complaining about tightness in his knee. Further tests showed a deeper problem, which meant he had to undergo surgery.

"Nemanja Vidic has had a meniscus operation on his right knee and will be out for around eight weeks," United said in a statement.

"Sir Alex, as a precautionary measure, rested Vidic at the weekend, after he complained of tightness in his knee, however, further medical investigation revealed the underlying problem.

"The central defender was operated on this week and will be sidelined for about eight weeks."

Meanwhile, Jonny Evans has backed youngster Michael Keane to make his mark in the League Cup, where United begin their campaign against Newcastle United Wednesday. "I've been really impressed with young Michael Keane," Evans told the club's official website.

"I think his brother has been getting more of the headlines over the last couple of years. Will's also a fantastic player but obviously he's got an injury at the minute.

"I've been really impressed with Michael when he's stepped up into training with us and I can see him getting a bit of a run-out if things go well."

Evans believes the League Cup gives youngsters a chance to shine. "Last year, I was captain of the team that got beaten by Crystal Palace," Evans said. "Although I don't like saying that.

"It was an honour to be captain but we lost that game. It was quite a young side we had out that night but I'm sure the manager will juggle it and make sure he picks a team that can win the tie.

"We won the League Cup two years in a row not that long ago, because it was along the lines of the manager giving the young lads a chance and, to be fair, he did stick with it all along the way. It was the first trophy I won at the club and he stuck with the young players that time.

"I'm 24 now and I just feel like I've gained a lot of experience over the last couple of years. Hopefully I can pass that on."