Baleba is one of the finest young midfielders in Europe
Carlos Baleba's stunning effort decided an enthralling five-goal game at Amex Stadium and gave Brighton a first Premier League win in six matches.
The midfielder curled the ball into the top corner in added time to decisively swing the pendulum in the direction of Fabian Hurzeler's team.
Yasin Ayari had given the home side the advantage in the first half with a brilliant strike before a second-half comeback from the Hammers looked to have turned the game on its head.
Mohammed Kudus restored parity soon after half-time with a close-range finish before Tomas Soucek powered home a header.
The home side rallied though, and levelled through Kaoru Mitoma before, almost the final kick of the game, Baleba fired powerfully past West Ham goalkeeper Alphonse Areola from outside the box.
The opening stages of the game showed why Brighton and West Ham went into the game as two of the out-of-form sides in the Premier League.
Ayari injected some much-needed quality in the 13th minute though, curling the ball into the top corner from the edge of the box.
The goal energised the hosts, who thought they had gone two ahead until Simon Adingra's strike was ruled out for offside.
Soucek almost levelled for the Hammers but Bart Verbruggen turned the ball onto the crossbar. He was beaten soon after half-time however, when Jarrod Bowen squared for Kudus to finish with ease.
Brighton looked more likely to grab a late winner as the half wore on but Soucek headed in Bowen's cross at the back post with seven minutes to go, putting Potter's team on the verge of an impressive comeback victory.
Brighton were far from done though and netted twice in three minutes - first with Mitoma's header and then with Baleba's unstoppable shot - to snatch an unlikely victory and end their run of modest form.
The Seagulls move up to ninth in the table and West Ham remain in 17th, one place above Ipswich but with their Premier League status assured for next season because the Tractor Boys lost at Newcastle United and have been relegated.
Potter reacts to defeat at Brighton
West Ham struggles continue under Potter
When West Ham hired Graham Potter in January, the expectation from many fans was that he would coax the same fluid football that caught the eye when he was in charge of Brighton from a talented Hammers squad.
But the loss at the Amex means the Hammers have still only won three times in the 14 Premier League games under the former Chelsea boss.
Jarrod Bowen's form has papered over the cracks for the London club in 2025 and they once again struggled to create if their captain was not involved.
Bowen assisted Kudus' leveller and Soucek's header in the second half – his fifth and sixth in the league this term – and he has more goal contributions than any of his team-mates in 2024-25.
Bowen said after the match: "It's gutting. To lose the game in that manner is sickening. But we have to look at ourselves.
"This is not the first time we have been in a winning position and not picked up points. This is the Premier League, you have to be on it."
If Ipswich had not completed the trio of sides to be relegated from the top tier this season already, the Hammers could have been put under real pressure.
Imprinting his style since replacing Julen Lopetegui mid-season was always likely to take time, but Potter knows the points tally since he arrived at West Ham is a long way from acceptable.
"The ability to sustain [our performance] is the biggest factor," said the ex-Brighton manager.
"We did a lot of good things. We have been done by two goals from outside the box. We created chances, scored two goals, but you need to sustain that and that is the challenge for us.
"We have lost, thrown points away at the end and we are hurting.
"We have to acknowledge the season we are having is a bad one. The fact we have stayed clear of relegation is good but not good enough. We have to do better".
How Potter's West Ham lacked mentality - Houghton
Baleba is Brighton's latest find
Baleba has been impressive for Brighton this season and Saturday's performance against West Ham was another example of that.
Not only did the 21-year-old score the stunning last-gasp winner, but the Cameroon international snuffed out West Ham's advances on many occasions and was a key link between defence and attack for the hosts.
The midfielder was signed by Brighton from French side Lille in 2023 and his emergence helped the Seagulls deal with the departures of Moises Caicedo, Yves Bissouma and Alexis Mac Allister.
In January, former Brighton striker Glenn Murray said Baleba had "even more potential than Yves Bissouma and Moises Caicedo" and he is established as one of the key components in Hurzeler's team.
His form is likely to have teams in the Champions League circling this summer for an all-round midfielder with no apparent weaknesses.
Brighton's Hurzeler reacts to win against West Ham
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