Wayne Rooney and Robin van Persie fired the home side into a 2-0 lead before Hammers striker Diafra Sakho halved the deficit before half-time at Old Trafford.
The United captain received his marching orders for a reckless challenge on Stewart Downing in the second half, leaving his side a man down for the final 32 minutes.
Here is a selection of our favourite Twitter reaction from the professionals after what was ultimately an unconvincing United win.
Tottenham Hotspur legend Gary Lineker (@GaryLineker) can’t believe Rooney’s moment of madness: “Wayne Rooney in a moment of lunacy, kicking out at Downing, gets a red card.”
Former United defender Philip Neville (@fizzer18) praises debutant Paddy McNair: “Big win for Utd after last week hung on in there at end with 10 men – great debut by Paddy Mcnair at the back vs physical team!”
Red Devils legend Edwin van der Sar (@vdsar1970) is hoping Van Gaal’s side can take much-needed confidence from the win: “At last 3 points @ManUtd for a change and hope this will kick start the season! TV switched back to @FOXSportsnl to watch @AFCAjax.#nacaja”
United legend Bryan Robson (@bryanrobson) is thrilled for the manager: “Considering all the injuries great result, congratulations Louis!”
Former Southampton man Richard Chaplow (@Rchap04) pays tribute to United’s new signing: “@LukeShaw3 well in buddy”
Finally, more from Lineker (@GaryLineker): “Just interviewed Louis Van Gaal. You can see it on MOTD tonight.”
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