For Sir Alex Ferguson's birthday on New Year's Eve his players gave him the present he has most wanted: a clean sheet. This was only the fourth time Manchester United's rearguard has not been breached in the Premier League and with Ferguson's "warrior" defender Nemanja Vidic coming through a second start since mid-September and a seven-point lead at the top there is much to make the Scot's champagne fizz as he turns 71 on Monday.

Ferguson has been at a loss to fix or explain why United have conceded 28 goals this campaign. Maybe now a fresh frugality in front of their own goal can be United's new year resolution.

Patrice Evra led the queue of senior players who want to build on this display. "After the drama of the Newcastle game [which Manchester United won 4-3] it was the sort of gritty win you need in a title race," he told MUTV. "It was an unbelievable game against Newcastle but today was more about not conceding a goal and a solid performance. We finished with a clean sheet and the three points. That was the most important thing.

"It is good for the confidence to keep a clean sheet. But I am more worried about winning games than conceding goals. I'm a defender, I don't like to concede goals, but it is not only about the defence it is about the whole team. I know that when we have a big game – when we play Arsenal, Chelsea or [Manchester] City – the defence is always strong.

"Maybe this is going to sound a bit bizarre what I am going to say: I feel we were more awake defensively last season and we conceded less goals but this season every time our opponents shoot they always seem to score. I know sometimes it is about our concentration and we can do much better but I'm not worried about that, I'm just worried about winning games."

Ashley Young, whose ninth-minute cross was deflected in by the West Bromwich Albion defender Gareth McAuley for United's opener before Robin van Persie's impressive finish at the close settled home nerves, said: "As soon as Robin got the second goal, the game was over but we defended brilliantly. The back four and the keeper were fantastic today. Getting a clean sheet is brilliant. Every one of them at the back was fantastic and deserve a pat on the back and a clean sheet for how much work they put in.

"It wasn't an easy pitch out there. It was boggy and everybody will be tired tomorrow because they put in a good shift. I don't think we wanted that drama again after the other night [against Newcastle]. We wanted to get off to a good start, which the manager said, and we managed to do that."

Perhaps in a sign of the times for Rio Ferdinand, Jonny Evans was preferred alongside Vidic, with the ex-England captain watching from the bench. With Phil Jones and Rafael da Silva back in contention for the trip to Wigan Athletic on Tuesday, and Chris Smalling performing well at right-back against West Brom, Ferguson suddenly has an embarrassment of defensive options.

Evans said on Saturday: "At the start of the season there were occasions when myself and Rio were playing most of the games when we had a lot of injuries. It's good to have the other lads back. It's not only competition for places, it's more that there are so many games. It's almost impossible to play every single game – you'd end up forcing injuries upon yourself by placing demands on your body.

"We definitely see it as benefit having everyone back fit – it strengthens the squad and provides competition so that everyone's playing at the optimum level."

Ferguson also responded to speculation regarding the future of Nani by claiming he will not be sold in this month's transfer window and the Scot described reports he will sign the Borussia Dortmund forward Robert Lewandowski as "absolute nonsense".

Of the defeat Steve Clarke, the West Bromwich manager, said: "I am disappointed not to get anything from the game because I expected a positive result. Maybe it shows you where we are as a club and as a group, and how much we think we have improved."

Man of the match Michael Carrick

(Manchester United)