West Ham came crashing back down to earth after Brentford ran out 2-1 winners at the London Stadium thanks to Yoane Wissa's stoppage-time winner.
The Bees were hot out of the traps against a sluggish Hammers who, perhaps because of their Europa League endeavours in midweek, took a good 35 minutes to get going.
Bryan Mbeumo fired the first warning shot, clipping the crossbar a couple of minutes in with a curling left footed shot, and he should have scored moments later, planting a header wide from six yards out after great work from Rico Henry.
Ivan Toney then tested the athleticism of 36-year-old Lukasz Fabianski, and the Pole showed why he's so far kept Alphonse Areola on the sidelines this season - getting down sharply to keep out a low drive at his near post.
Brentford's dominance continued and they were rewarded with the opening goal on 21 minutes. Toney's defensive-splitting ball to Sergi Canos produced another fine save from Fabianski, but he could only palm the ball out to Mbeumo - who turned the ball over the line, just, from an acute angle.
Goal-line technology confirmed the ball had crossed the line, and it was seemingly the shot in the arm West Ham needed to come to life.
Said Benrahma had the hosts best chance in the first half, firing wide from outside the box after good hold-up play from Michail Antonio, before his free kick just after the break was spectacularly tipped over by David Raya.
The Hammers then assumed complete control, piling forward in front of a capacity crowd. Jarrod Bowen really should have scored, glancing a header wide from Vladimir Coufal's cross, before Pablo Fornals had an effort well blocked by Ethan Pinnock after brilliant work from Antonio.
The home side continued to push, although they struggled to test Raya in Brentford's goal. Their never say die attitude was rewarded with ten minutes to go, as Bowen superbly steered a half-volley into the bottom corner after Aaron Cresswell's corner was half cleared.
But the drama didn't finish there as Wissa, a late substitute, fired home unchallenged after Pontus Jansson's header had been kept out by Fabianski.
Here's how both sides rated.
West Ham player ratings
1. Goalkeeper & Defenders
Lukasz Fabianski (GK) - 7/10 - Saved superbly from Toney early on and was incredibly unlucky to see his fingertip save from Sergi Canos fall into the path of Mbeumo. Even then he almost saved the rebound.
Vladimir Coufal (RB) - 5/10 - Unusually wasteful with his passing early on, asking far too much of Bowen. Grew into the game and became a threat running in behind Henry.
Kurt Zouma (RCB) - 5/10 - The better of West Ham's two central defenders - but still had a really tough time against Mbeumo and Toney. Booked in the first half after hauling down the latter.
Angelo Ogbonna (LCB - 4/10 - Showed his age for the first time in a West Ham shirt. Sucked out of position for Brentford's goal and looked off the pace against an energetic front duo who flipped roles as the deep lying and advanced forwards seamlessly.
Aaron Cresswell (LB) - 6/10 - Ensured West Ham were a threat from set pieces with superb deliveries into the box. A bit stretched early on defensively but helped level up what was a one-sided contest early on.
Declan Rice (CM) - 6/10 - It's not often that Rice is overshadowed, but Brentford's strength in numbers took him completely out of the game in the first half. Got more of a foothold as West Ham took control but far from his absolute best.
Tomas Soucek (CM) - 5/10 - Like Rice, Soucek found it difficult to cope with being outnumbered - often seeing his pressing bypassed by Brentford's ability to pick out a spare man.
Said Benrahma (AM) - 6/10 - A livewire. Benefitted from Antonio's hold-up play and took up some excellent positions in and around the box, while his presence centrally helped suck out one of Brentford's trio of centre backs.
Jarrod Bowen (RW) - 6/10 - Was frustrated in the first half as West Ham struggled to make the most of the possession they had. Ran his socks off, as per, and mixed in missing a golden opportunity with a superbly controlled equaliser.
Michail Antonio (ST) - 7/10 - Hustled, bustled and stretched Brentford's backline once the Hammers had remember. Hold-up play was great at times.
Pablo Fornals (LW) - 5/10 - Started to get West Ham firing, recognising he needed to come deeper to match up Brentford number wise. Not his best outing.
Brentford player ratings
4. Goalkeeper & Defenders
David Raya (GK) - 6/10 - Tipped over Benrahma's free kick early in the second half, but wasn't tested too much considering West Ham dominated after the break.
Mathias 'Zanka' Jørgensen - 6/10 - Assured and calm in everything he did. A very capable replacement for the injured Kristoffer Ajer and knows when to make a tactical foul. Booked.
Pontus Jansson (CB) - 7/10 - Was on top of things early doors as Brentford stifled West Ham's threat. Started to find it more difficult once Antonio came to life.
Ethan Pinnock (LCB) - 7/10 - Solid in defence and linked up well with Henry, particularly in the first half. Made a crucial block from Fornals.
5. Wing-Backs & Midfielders
Sergi Canos (RWB) - 7/10 - Exceptional early on as West Ham chased Brentford all around the park. Had more work to do defensively as the game went on but didn't shirk away from his responsibilities.
Shandon Baptiste (RCM) - 6/10 - Forced off with a shoulder injury when Brentford were well and truly on top.
Christian Norgaard (CM) - 8/10 - Scooped up absolutely everything in midfield. A gritty performance and one that allowed others to shine around him.
Frank Onyeka (LCM) - 6/10 - Often the spare man in Brentford's midfield three, helping transition defence into attack at speed.
Rico Henry (LWB) - 7/10 - Really bright early on, limiting Coufal's ability going forward as well as driving in behind at pace.
Bryan Mbeumo (FW) - 8/10 - Really, really good early on. Came short, drifted wide and ran in-behind at pace. Took his goal smartly and was unlucky with his early effort that clipped the bar.
Ivan Toney (FW) - 8/10 - Another sensational performance from Toney, particularly in the first half an hour. Zouma and Ogbonna couldn't cope with his movement, while his ball to release Canos through was brilliant.
Mathias Jensen (RCM) - 6/10 - Slotted in after Baptiste went off injured but soon found the tide of the game turning against him.
Mads Bidstrup (LCM) - N/A
Yoane Wissa (FW) - 7/10 - A late substitute, Wissa was alert to the danger in West Ham's box and fired an unstoppable effort past Fabianski.