Old Trafford survived a pitch inspection before Manchester United scratched their way past West Brom for a 2-0 win in the Premier League.
A ninth-minute own goal from Gareth McAuley set the hosts on their way, but having failed to extend that advantage when they had the better of play in the first half, they struggled in the second as the Baggies grew in confidence.
The visitors even hit the bar via a McAuley header with 20 minutes to play.
But Robin van Persie, brought on as a second-half substitute, scored his 14th goal of the season in the last minute of the match to settle any nerves.
It was a moment of class on a difficult afternoon, and ensured that Sir Alex Ferguson will celebrate his 71st birthday on New Year’s Eve with his side seven points clear of crosstown rivals Manchester City in the title race.
The headline news from the teamsheets was Ferguson’s decision to bench both Van Persie and Javier Hernandez – given Wayne Rooney’s absence through injury, that left the league leaders with Danny Welbeck up front, supported by the returning Shinji Kagawa.
United started brightly, the pitch playing far better than might have been expected given that there was a late pitch inspection to see whether the game could take place at all.
Sir Alex Ferguson’s side have regularly had to come back from losing positions this season, but struck early to give themselves control of the match.
The ball bounced Ashley Young’s way after an attempted flick forward from Kagawa deflected through to him, and his fiery low cross was turned in by McAuley.
United pressed forward with confidence, Welbeck testing Ben Foster as the home side enjoyed almost three-quarters of the possession.
Foster was called into action on more than one occasion, making an impressive pair of stops to deny Young on the half-volley, and then again to help parry Michael Carrick’s effort from the resulting corner.
However, perhaps losing his footing, he almost allowed Welbeck an embarrassing goal after clumsy control of a passback.
Certainly, the signs did not point to a West Brom resurgence in the second half, but the Baggies have shown steel under Steve Clarke to still be in the mix for a Champions League place at the halfway stage of the season, and grew stronger as the rain started to pour down.
Their chances were limited to hits from distance for the most part, but they enjoyed more possession in the second half than their hosts, and once they introduced Romelu Lukaku up front looked capable of scoring.
In fact, only the woodwork denied McAuley atoning for his own goal with a headed effort from a corner.
United had their own opportunities, but they were fewer and further between. Antonio Valencia drew a save from Foster at his near post early on, Van Persie and Welbeck both saw shots in the final 10 minutes smothered and saved.
Foster could not keep holding out United, though, and it took a curling, whipped effort from the Dutchman to finish the contest. The relief around Old Trafford was palpable.
They will start 2013 in great shape to push for a 20th league title after taking seven points from nine so far over Christmas.
MAN OF THE MATCH
Tom Cleverley (Manchester United) – Wide range of passing and control, linking up well with Kagawa and Welbeck in the first half, particularly.
MANCHESTER UNITED: De Gea 7; Smalling 7, Evans 7, Vidic 7, Evra 6; Valencia 6, Carrick 6, Cleverley 8, Young 7; Kagawa 7, Welbeck 6 – Subs - Van Persie 8, Scholes (N/A)
WEST BROM: Foster 8, Jones 7, McAuley 6, Tamas 6, Ridgewell 6, Thorne 5, Brunt 6, Rosenberg 6, Dorrans 6, Odemwingie 7, Long - Subs – Lukaku 7, Morrison 7, Fortune (N/A)