By Jamie Jackson/The Guardian

United secured their passage into Champions League quarter-final with a 3-0 victory over Olympiakos on Wednesday night courtesy of a Robin van Persie hat-trick, but the Dutchman sustained second-half injury and has been ruled out of action for four and six weeks with a sprained knee, giving manager David Moyes a cause for concern. The Dutch international, 30, was taken off on a stretcher. Rooney, however, insists the team have to produce similar performances on a consistent basis if they are to salvage anything from a bitterly disappointing campaign.

“We have to. That’s been part of our DNA over the years I’ve been here that intensity, that running off the ball, the pace we play at,” the striker said. “It’s a big part of the way we play and it showed that when we do that to teams it’s difficult for them to stop us. I think we’re spurred [on] by the way the games and results have gone. It’s not necessarily the comments which people have made, it’s more the fact that we’re not getting the results and as a team it’s hard to take so we’ve kept working and hopefully it’ll get better.

“It was a good performance. I think the performance and the result were much needed. It was a massive game for us. We came out with a great attitude and fully deserved the victory.

“After the first game in Athens and especially what happened on Sunday (losing 3-0 to Liverpool at Old Trafford), we knew that we had to come and give a big performance, for ourselves really  for our own personal pride and [for] the manager, and we’ve done that. I’ve said before our performances this season haven’t been good enough and we owe the manager a big performance, but we know as players we are better than what we’ve done this season.

“As a group we have to show that and put it right. It’s something we have to kick on from now. We’ve still got a few games left in the season and we want to build on this. Hopefully we can do that.”

Ferguson’s departure key factor

United are 18 points behind the Premier League leaders, Chelsea, and 12 from a Champions League berth, with nine matches left. Rooney believes the departure of Sir Alex Ferguson in the summer is a key factor in the disappointing season. “It was always going to be tough when Sir Alex left,” he said. “It was obviously a massive change so we knew it was going to be tough but we didn’t expect it to be as tough as it has been. But we have to put that right. We have to keep working, keep believing in ourselves and hopefully it’ll get better.”

He also backed Moyes’s claim that despite being firm underdogs United could yet win the Champions League, much as Chelsea did in 2012 and Liverpool in 2005. “Yeah. In cup football anything can happen. With a bit of luck hopefully we can go far,” said Rooney.

Ryan Giggs, who was inspirational against the Greeks in his first start for two months, downplayed any suggestion United could be facing the end of their era of domination, like Liverpool in the early 1990s.  “Well, you can see why people are saying that because we haven’t produced it this season on a regular basis,” the Welshman said. “I know from experience what these players are capable of and a lot of them have been written off. I think there is a lot of quality within the dressing room.”

Giggs also admitted he wanted to feature more. “I hope so, yeah, I have probably not played as much as I would like in the last few months,” he said.

Van Persie’s three goals took him to 14 in 23 United matches this season, and Moyes will miss him the most.  Moyes had said an initial scan was “inconclusive” but a second look revealed the extent of the damage. Van Persie will now miss both legs of United’s Champions League quarter-final against Bayern Munich.

Ahead of seventh-placed United’s trip to Upton Park to face West Ham today, Moyes said he felt he could “look in the face” of home supporters again after beating the Greek champions to reach the Champions League last eight to face the current holders.

The Red Devils are 12 points adrift of the top four - and Champions League qualification - after last weekend’s 3-0 defeat by Liverpool at Old Trafford. “We had given them something to shout about. There was nothing to be ashamed of about our performance,” said the ex-Everton boss, who replaced the retired Sir Alex Ferguson last summer.

“In some of the games I have felt ashamed because we haven’t played well enough and I have not got a team out that has got a good enough result.”

Guardian News Service