MANCHESTER, United Kingdom (AFP)—Manchester United crashed out of the FA Cup with a meek 2-1 home defeat to Brighton on Sunday as Gabriel Martinelli’s hat-trick fired Arsenal to a 4-1 win at Portsmouth to reach round four.

United interim boss Darren Fletcher could only watch on in horror as the Red Devils’ last chance of silverware this season and likely his chances of landing the job until the end of the season went up in smoke at Old Trafford.

Fletcher’s men were left to rue not making more of a positive start before Brajan Gruda fired the visitors in front on 12 minutes from Danny Welbeck’s cross.

The roles were reversed midway through the second half as Welbeck lashed into the top corner against his former club.

There were persistent chants targeting United co-owners the Glazer family and British billionaire Jim Ratcliffe as the discontent at Old Trafford grew.

And any hope those in charge of the club had for a bounce following the removal of Ruben Amorim has proved very short-lived.

United will play only 40 games this season after exiting both domestic cup competitions at the first hurdle — their lowest number since 1915.

“I think you could see the players are fragile but they’ve got to respond,” said Fletcher.

“This team is still good enough to achieve success this season but they have to dig deep.”

Benjamin Sesko’s late header set up a grandstand finish, but a red card for teenager Shea Lacey in stoppage time for dissent rounded off United’s miserable afternoon.

– Martinelli ‘talking on pitch’ –

Martinelli shrugged off the backlash to his clash with stricken Liverpool defender Conor Bradley as Arsenal reached the fourth round for the first time in three years.

Championship side Portsmouth were dreaming of an upset against the Premier League leaders when they went in front after just three minutes through Colby Bishop.

Mikel Arteta had made 10 changes from the side that drew 0-0 with Liverpool on Thursday.

Martinelli drew stinging criticism for trying to push Bradley off the pitch in the closing stages after the Northern Irishman hit the ground with a serious knee injury.

Liverpool confirmed on Sunday the right-back will need surgery and will miss the rest of the season.

The Brazilian apologised to Bradley after the game and did not seem affected by the furore at Fratton Park.

“That’s personality, come in and talk on the pitch,” said Arteta.

“To play for a big club you need a big personality because it can be that (being at the centre of a controversial incident), it can be an action that you miss, it can be something that costs you a game, and three days later there is a game, so you need to lift yourself up and make it count.”

Arsenal could rely on their threat from set-pieces to turn the tie around.

The Pompey lead lasted only five minutes as Andre Dozzell turned into his own net under pressure from Christian Norgaard.

Martinelli then flicked in the first of his three goals before Noni Madueke missed the chance to make it 3-1 from the penalty spot when the England international fired wide.

Gabriel Jesus teed up Martinelli to kill the tie off early in the second period before he completed his hat-trick from another Arsenal corner.

West Ham eased the mounting pressure on Nuno Espirito Santo as new signing Taty Castellanos scored his first goal for the club to beat QPR 2-1 after extra-time.

Castellanos has been signed to dig them out of trouble at the bottom of the Premier League and the £26 million ($35 million) arrival from Lazio bulleted home a header from Crysencio Summerville’s cross to secure a much-needed win.

Leeds needed a second-half fightback to beat Derby County 3-1 and book their place in the fourth round.

League One Mansfield held off Sheffield United to book their place in round four with a 4-3 win at Bramall Lane.

Norwich, Hull and West Brom also progressed to the last 32.