Just two minutes after picking up his first for blocking a quickly taken free kick, he cynically tripped Darren Fletcher and referee Mike Dean had no choice but to send him off.
With the man advantage West Brom finished the half strongly, however United almost went in to the break ahead, but Marcus Rashford’s low shit was deflected narrowly wide.
In the second-half United started strongly, with Jesse Lingard causing problems on the left-hand side.
But the Red Devils were behind in the 67th minute. Sebastien Pocognoli crossed to Rondon, who took a good first touch and fired home low past David De Gea.
Louis van Gaal’s side looked desperately for an equaliser, but despite having the majority of play, they failed to create any clear-cut chances, and West Brom held out for for three points to move up to 11th in the table.