United, already crowned Premier League champions, looked set to mark Alex Ferguson's last game in charge with an emphatic victory when they led 5-2 with 10 minutes to play, but the hosts hit back in stunning fashion to level it at five apiece.
And West Brom sprung another surprise on the title holders with a 2-1 triumph at Old Trafford in September, but the trend since then has been one of declining fortunes for the Midlanders.
Just one point separates Mel's men from the bottom three and, worse still, 18th-placed Sunderland have a game in hand.
The visitors do not have any relegation issues to concern themselves with, but David Moyes' charges are in unfamiliar territory.
Since the advent of the Premier League in 1992, United have finished in the top three every season, and yet this time around they sit seventh, well short of the division's leading sides.
Hopes of achieving qualification for Europe now hinge on United securing a spot in the top five, although sixth is likely to be good enough after Manchester City's League Cup success.
Moyes' old club Everton occupy sixth at present but have only a slender three-point advantage, with the two set to meet at Goodison Park on April 20.
West Brom, meanwhile, will not be able to call on striker Nicolas Anelka, who is under a club suspension as he awaits the final decision on how long his Football Association-sanctioned ban for his controversial 'quenelle' gesture will be.
