Manchester United cannot shake the habit of allowing opponents to score first, though when it is an own goal after only nine minutes it tends to kill the game. At least chasing a lead generates drama and a bit of atmosphere. Being handed an early one by a side with initially limited attacking ambition made for a fairly flat end to 2012, though doubtless Sir Alex Ferguson would argue a routine win to preserve a seven-point lead at the top is infinitely better than last season's New Year fiasco, when United were beaten at home by bottom-club Blackburn.

Not that this win was exactly routine, for before Robin van Persie's elegant goal in the 90th minute United were looking increasingly likely to be pegged back. Both sides had key players missing, and even with Wayne Rooney unavailable United felt able to leave Van Persie on the bench and let Danny Welbeck lead the line.

It was hardly a success and nor was it a recipe for high excitement. Ferguson perhaps felt there was too much of that in the last game against Newcastle, yet the lack of it possibly explained why the Old Trafford hoardings kept advertising the fact that remaining tickets for the visit of Liverpool in January are proving a hard sell.

Ferguson blamed the soggy pitch for killing the game but admitted he will change the team around again on Tuesday. "We'll get another tough game at Wigan, they had a great result today," the United manager said. "Robin van Persie is a fantastic player to be able to send on, he changed the game for us."

Steve Clarke did not disagree with that assessment, he took it as a compliment. "The fact they had to send on one of their big guns shows how well we were playing," the West Brom manager said.

United survived a penalty scare when Chris Smalling collided with Shane Long on West Brom's first attack but took the lead five minutes later. After playing a one-two with Shinji Kagawa on the left Ashley Young's low cross was deflected past his own goalkeeper by Gareth McAuley.

In his first game for two months, Kagawa almost set up a second for Young on the half hour, when his perfectly weighted pass down the right wing invited an Antonio Valencia cross from which Young brought a first-class save from Ben Foster. If that was sharp from the former United goalkeeper, Foster was ponderous on the stroke of the interval, allowing Welbeck to charge down a clearance and watching with relief as the rebound rolled to safety instead of into an empty net.

Chris Brunt had a long shot saved at the start of the second half then saw a better effort blocked by Patrice Evra, as United's attempts to score a second descended into farce. Young's air-shot from near the penalty spot was perhaps the most inept squandering of a decent chance, though Welbeck and Kagawa also lacked confidence and finesse in front of goal. After 65 minutes Ferguson had had enough and sent on Van Persie, just in time to see McAuley hit the bar from a corner.

By this stage the team in front were fighting a rearguard action and struggling to cross halfway, while the away fans were the only ones making any noise, alternating between observing how sepulchral the silence was and mocking Ferguson for his assertion that Van Persie "could have been killed" at Swansea.

After seeing one shot saved Van Persie finally delivered at the end, making space for a left-foot curler from the edge of the area after a Paul Scholes effort had been blocked. Do not be fooled though. Between the goals, United were so laboured it made a mockery of Ferguson's claim that he has all the players he needs this January. If so, some of them seem weary. As Tony Coton told his MUTV audience on the whistle, the game was a perfect advertisement for a winter break.