United, who were missing influential midfielder Kalvin Phillips with a knee injury, struggled to create chances against the Seagulls, who just about sealed their own top-flight status for another year.
Defeat for the West Yorkshire club brought to an end a six-game unbeaten streak – their best top-flight run since the days of David O’Leary in November 2001.
Head coach Marcelo Bielsa was frustrated that his side struggled to threaten, with top scorer Patrick Bamford denied service before being substituted just before the hour mark.
“We had a problem in the creation prior to the ball reaching Patrick, where he had no influence and he could not receive the ball in positions where he can cause harm to the opponents,” said Bielsa.
“Our offensive game was weak. I always hope we can compromise them by creating more danger.”
United winger Jack Harrison refused to use Phillips’ absence as an excuse for the loss.
He’s done excellently and he’s a massive part of our team,” said Harrison. “We’ve got some great players on the bench that can step in and add different aspects to the game as well.
“You saw today in the middle they added some things that we might have been missing. Kalvin is a brilliant player for us and breaks up a lot – he’s obviously key to how we play but those players came in and work hard. I thought they did well.”
Asked whether Leeds were still looking at the European places after the defeat, he said: “We’re an ambitious team, we’re always pushing to break our limits and the European places are something we’re definitely looking forward to. It’s difficult, we’ve had a great season so far and it’s easy to get caught up in everything. We’re not finished yet and we’re going to keep fighting until the end and see how well we can do.”
Albion manager Graham Potter, the former York City left back said it was a shame there was no crowd to witness Danny Welbeck’s sublime goal against the Whites.
Former England forward Welbeck sealed the win after executing a perfect Cruyff turn on a dropping ball.
Pascal Gross’ early penalty, after a clumsy challenge set Albion on course for only a third home league win of the campaign, which moved them on to 37 points and piled further pressure on 18th-placed Fulham.
Potter said: “It was a great bit of quality from Danny to get it.
“It’s one of those moments when you are just sad that there’s not a crowd there to enjoy it live because it would have been an off-the-seat moment.
“The turn itself was a great football action and then to finish it off as well as he did is great for Danny.”
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