United twice fought back from a goal down, with substitute Marouane Fellaini cancelling out Stephane Sessegnon’s early opener with his first goal for the club, while Blind fired in an 87th minute equaliser after Saido Berahino had restored the lead for West Brom.
Louis van Gaal had insisted beforehand he was pleased with the progress after steering United within touching distance of the top four, but they remain 10 points adrift of leaders Chelsea, while Alan Irvine’s side edged further from the bottom three.
There had been little goalmouth incident in a frantic opening until Andre Wisdom left Angel di Maria in his wake in the eighth minute. The defender set off on a driving run from his own half, with no interruption, and his low cross was met with a superb first-time finish from Sessegnon which flew into the top corner.
Suddenly United’s defensive frailty, so evident in their opening games, was there for all to see and James Morrison lashed over following more jittery work from the backline.
Di Maria has provided plenty of attacking artistry since his move from Real Madrid, but for once he unleashed an ugly, scuffed effort that failed to trouble Boaz Myhill.
The energetic Wisdom then cut out a dangerous cross from Robin van Persie as United gave another glimpse of their threat, but Juan Mata made a mess of a promising free-kick, ballooning the ball over.
Just before the break, United’s night nearly worsened when Joleon Lescott nodded over and a concerned Van Gaal appeared to issue orders to Fellaini as both teams trooped off.
Fellaini, one of the few remnants from the short David Moyes reign, came to the aid of his successor after only two minutes of the second half. Di Maria sent over a swirling cross to the tall midfielder and he shrugged of the attentions of Lescott, turned swiftly and drove a rising shot past Myhill.
United’s skittish players had been injected with fresh belief and Mata’s goal-bound shot was blocked as they searched for more.
But Berahino revived the hosts with a ruthless finish. Chris Brunt slid the ball through a gaping hole in the United defence and the striker raced into space and calmly placed the ball past David de Gea.
There was more dismay amidst the United ranks as they appealed in vain for a penalty after Sebastien Pocognoli handled and Van Persie then hit the post with a dipping effort from outside the area.
But Blind kept his composure late on, guiding a low shot into the bottom corner after Lescott had only partially cleared a cross from Rafael.