Jarrod Bowen scored a hat-trick as Brentford were beaten 4-2 by West Ham United at London Stadium on Monday night.
The Bees were 2-0 down inside seven minutes, when Bowen netted twice from inside the penalty area.
Neal Maupay pulled a goal back for the visitors on 13 minutes, but goals in the second half from Bowen, his third of the night, and a long-range hit from Emerson put the game beyond Brentford's reach.
Yoane Wissa reduced the deficit with 10 minutes to play, assisted by fellow substitute Mikkel Damsgaard.
Maupay pulls one back for Brentford after Bowen's early brace
Thomas Frank made three changes to the Brentford side that lost 1-0 to Manchester City last Tuesday: Mads Roerslev, Vitaly Janelt and Yoane Wissa made way for Keane Lewis-Potter, Mathias Jensen and Neal Maupay.
West Ham also made three switches from their defeat to Nottingham Forest in their last fixture, as playmaker Lucas Paquetá came in for his first appearance since 7 January. Konstantinos Mavropanos and Tomáš Souček also came back into the starting XI having been on the bench against Forest.
The visitors had the better of the opening stages and should have taken the lead inside five minutes. A Vladimír Coufal cross was flicked on by James Ward-Prowse but, when it dropped to Souček inside the six-yard box, he blazed over from close range.
But the Hammers' early dominance eventually told, as they quickly took a two-goal lead. First, a move down the left saw Emerson cut back to Bowen, who fired off the near post and into the back of the net.
Then, an almost identical move down the right saw Bowen net a second. It was Vladimír Coufal this time who squared from the flank to the England international, and Bowen finished again from inside the penalty area.
Brentford pulled one back with 13 minutes on the clock, as Maupay made it 2-1. A clever pass from Ivan Toney into Keane Lewis-Potter saw the Bees progress into the final third. When the wing-back poked a pass through to Maupay, the Frenchman slid in and finished cooly past Alphonse Areola.
The game quietened down after the frantic start, with both teams having spells of possession.
West Ham had a few half-chances through Lucas Paquetá and then two from Mohammed Kudus. The first two were volleyed wide before the third was saved comfortably by Mark Flekken.
Wissa nets late consolation as substitutes combine at London Stadium
Brentford started the second half brightly, with Lewis-Potter a bright spark down the right. It was his cross that almost found Toney inside the penalty area, but the striker couldn't quite connect with a diving header.
But David Moyes' side doubled their advantage just after the hour mark, when Bowen netted his hat-trick. The ball came in from a wide area again, this time from Kudus, and the Hammers forward ghosted between Kristoffer Ajer and Zanka to head home.
It was 4-1 soon after, when Emerson fired in from 30 yards. A Kudus cross was headed out by Onyeka, and it fell straight to the full-back who arrowed an effort into the top corner.
Wissa pulled one back for Brentford with 83 minutes on the clock, when some nice play from substitute Damsgaard saw him feed his team-mate, who curled a fantastic finish into the bottom corner.
The Bees pushed for another as the game ticked on. Toney's header was clawed off the line by Areola and Damsgaard's near-post effort forced the West Ham keeper into a smart stop.
West Ham: Areola, Coufal, Zouma, Mavropanos, Emerson, Álvarez, Souček, Kudus (Johnson 90+4), Ward-Prowse, Paquetá (Antonio 77), Bowen
Subs not used: Fabiański, Scarles, Aguerd, Ogbonna, Earthy, Ings, Mubama
Brentford: Flekken, Ajer, Zanka, Mee (Collins 61), Lewis-Potter, Onyeka (Janelt 73), Nørgaard, Jensen (Damsgaard 77), Reguilón (Roerslev 73), Maupay (Wissa 73), Toney
Subs not used: Strakosha, Ghoddos, Baptiste, Yarmoliuk
Frank: We didn't hit our level
Brentford head coach Thomas Frank expressed his disappointment at the Bees’ defeat to West Ham.
He admits the west Londoners "didn't hit their level" against the Hammers, but attempted to find some positives from the loss at London Stadium.
“I feel terrible. My body is burning and I feel terrible, absolutely terrible,” he said.
“Individually and collectively, we didn't hit our level today and, if you don't have the level in this league against any team, and this is a very good West Ham team, with [Jarrod] Bowen that was unplayable and Emerson deciding to put in the top corner, then it's very, very difficult to win.
“Of course, it's very disappointing but, in every game, it's never as bad and never as good.
“It feels very bad but, when I look at it back, I'll find more positive and that’s what we’ll hang our hat on. And then we’ll try and adjust those negatives.”
Lewis-Potter: Sloppy start cost Brentford
Keane Lewis-Potter rued Brentford’s “sloppy” start at London Stadium, which saw the Bees two goals down inside the opening seven minutes.
“It’s hugely disappointing,” he said.
“We started the game very sloppy, and you can’t do that in the Premier League. You can’t expect to get points from the game and today showed that.
“With the position we’re in now, the most important thing is getting points on the board. We didn’t do that today.”