It's fair to say that Manchester United were not at their best against Brighton & Hove Albion.Jose Mourinho's men  put in a quite dismal performance as they succumbed to a 1-0 defeat at the Amex Stadium on Friday night.Man United were well under par as they endured a miserable first half. They could, and maybe should have found themselves behind, but had David de Gea to thank for a couple of smart saves.But he was finally beaten in the second half as Pascal Groß headed home to score the only goal of the game in the 57th minute.The result is unlikely to have any impact on Man United's Premier League finish, with Mourinho's men still odds-on to finish second.But the performance, especially in attack, will be cause for concern.

WHAT MAN UNITED FANS SAID ABOUT ROMELU LUKAKU

Romelu Lukaku has almost been an every present for Man United this season.

He has featured in 50 games in his debut season in Manchester, scoring 27 times.

But he was not available for the game against Brighton after picking up an ankle injury against Arsenal last weekend.

Despite not playing, United fans still had a lot to say about him on Friday night.

Marcus Rashford started in Lukaku's place up front, and, to put it lightly, he did not have his best game.

Rashford could do very little right as he struggled in Lukaku's position.

To be fair to the 20-year-old, it wasn't just him who struggled. Anthony Martial and Juan Mata were largely ineffectual for the whole game, whereas Paul Pogba also struggled to create.

So what did that make Man United fans realise?

Well, Man United's dire performance against Brighton, and especially Rashford's, made supporters realise just how important Lukaku is to the team.

The Belgian striker has had an impressive season in front of goal for his side, but he often doesn't get the credit he deserves.

But even though he didn't play on Friday night, he was still one of the biggest talking points of the game as fans realised just how crucial he is to the team's style of play.

TWITTER REACTS

Although not in the circumstances that he would have imagined, it's good to see the Belgian striker finally getting the credit he deserves.

WILL LUKAKU START IN THE FA CUP FINAL?

After their showing against Brighton, fans will undoubtedly be praying that Lukaku recovers from his injury in time to face Chelsea in the FA Cup final on May 19.

Although Mourinho is hopeful that he will play, he admitted that he does not know at this point in time.

"I don’t know [if he'll be fit for the FA Cup final], I just know that of course he’s not fit for tomorrow," he said prior to the Brighton game on Thursday. "We must wait for more scans and more time. But not tomorrow.

"I hope so. It looks possible."