United signed off for the international break almost a fortnight ago with a 0-0 draw against Aston Villa, extending their winless run to five matches. The stalemate at Villa Park also marked a third successive league game without a goal for the Reds.
Manager Erik ten Hag, who is under great pressure, was granted a stay of execution by the United hierarchy during the hiatus.
United have won just two of their opening seven league matches this season and currently sit 14th in the table with eight points to their name. Brentford are three places and two points better off.
The Reds have won each of their last three home games against Thomas Frank's side, including last season's dramatic 2-1 triumph, and will be determined to make it four in a row this afternoon.
Follow the live blog below for regular updates and analysis from Old Trafford...
Brentford Take the Lead
It's all over here at Old Trafford and United are back on track!
They have beaten Brentford 2-1, courtesy of second half goals from Alejandro Garnacho and Rasmus Hojlund. Both goals were excellent and United's performance deserved all three points.
Next up is a midweek trip to Turkey to face Fenerbahce in the Europa League.
A Tense Second Half
There will be five additional minutes here at Old Trafford.
Erik ten Hag has just brought on Noussair Mazraoui, who has replaced Alejandro Garnacho.
ON: Ugarte, Lindelof
OFF: Casemiro, Evans
A late change is in the offing for United, with Casemiro currently down on the deck.
Matthijs de Ligt finds himself in space, drives forward, crosses from the right and finds Alejandro Garnacho, who fires straight at Mark Flekken.
United have been well on top since getting their noses in front via Rasmus Hojlund's 62nd-minute goal.
Despite that, it is likely most supporters will be nervous as we head into the closing stages of this game.
Casemiro takes aim from distance and it flies wide of the target. He fancied a crack.
Erik ten Hag is making his first change;
ON: Zirkzee
OFF: Hojlund
Brentford have also made a couple of changes, bringing on Fabio Carvalho and Yehor Yarmolyuk.
A storming run from Diogo Dalot almost results in a third United goal. He drives into the box, gets a shot off, but is denied by Mark Flekken.
United should be out of sight.
Brentford head coach Thomas Frank makes his first change of the game;
ON: Yoane Wissa
OFF: Keane Lewis-Potter
The comeback is complete!
Rasmus Hojlund dinks a lovely finish over Mark Flekken and United lead.
However this game finishes, there will be plenty of debate about the manner of Brentford's opener.
Ethan Pinnock headed the Bees ahead just before the break when United were a man light at the back after Matthijs de Ligt had been told to leave the field of play due to blood pouring down his face from an earlier head injury.
You can have your say on the goal via the poll below.
A Frustrating First Half
Brentford midfielder Christian Norgaard goes into the book after a foul on Alejandro Garnacho. He was a booking waiting to happen.
Alejandro Garnacho is causing so many problems for Brentford. He shoots to try and to add to his tally and is denied by a smart save from Mark Flekken.
United are well on top.
The question coming into this half was whether United have it in them to use the goal as rocket fuel for their performance this half. That is the perfect response. A great cross by Marcus Rashford and fine finish from Alejandro Garnacho. The keeper isn't too clever guarding his near post and Garnacho found the gap.
That's just the start United needed! Alejandro Garnacho brings United level with a fine finish.
That will do nicely!
The second 45 is off and running here at Old Trafford. United have got work to do.
The players are starting to emerge from the tunnel for the second half here at Old Trafford.
As soon as Matthijs de Ligt went off then and couldn't defend the corner, we knew this is a club where the ball is now bound to go in. Ruud van Nistelrooy got booked but United only have themselves to blame. De Ligt had to come off the pitch for a third time as his head was bleeding and that has been the protocol for years.
Tunnel cam footage was visible on the press screens and Darren Fletcher went berserk at the fourth official in the tunnel.
The half-time whistle is blown here at Old Trafford Brentford have a slender lead.
Here are Samuel Luckhurst's half-time player ratings...
Onana
Made a routine save. 6
Dalot
Not attacked much. 6
De Ligt
Soldiered on after head injury. 6
Evans
Put off Schade for Brentford’s early chance. 6
Martinez
Settled after a tricky start against Mbeumo. 6
Eriksen
Skied a shot over but it wouldn’t have counted. 6
Casemiro
Threaded some decent passes. 6
Rashford
Sporadically lively. 6
Garnacho
Had some decent openings. 6
Fernandes
Not reliable enough with the ball. 5
Hojlund
Grew into the game with some smart turns. 7
Brentford take the lead right before half-time through Ethan Pinnock. He heads home from a corner.
United are furious as Matthijs de Ligt was off the pitch to have blood mopped from his face.
There will be four additional minutes at the end of this first half because of the head injury Matthijs de Ligt sustained earlier in the half.
De Ligt is currently needing medical attention again with blood pouring down his head.
United's best chances falling to Alejandro Garnacho and there is very little conviction about them at the moment. His hot streak at the start of the season has petered out and he doesn't look particularly confident in front of goal at the moment.
The chances are coming for United but they are not being taken. Rasmus Hojlund attempts to find the corner from inside the penalty area but he got too much on the ball and it went wide.
That was a top turn by Rasmus Hojlund, who wanted a booking for Nathan Collins after the ball went dead, and a fine pass by Marcus Rashford before Alejandro Garnacho wasted that opening. There were hands on heads from the United substitutes before they offered encouraging applause.
What a chance for United! Christian Eriksen has to score, but he somehow manages to scoop the ball over the crossbar from about nine yards out. He had to score.
Five hours and counting. That's since United last scored in the league. Southampton's lead against Leicester means United are the league's joint-lowest scorers with winless Crystal Palace.
Andre Onana is called into action to make a save from Christian Norgaard. The ball was flying across Onana's goal and he has done well to turn it away.
Southampton's second goal means United are now the lowest scorers in the Premier League. Time to change that, of course, but not exactly looking too threatening at the moment. About to hit five hours without a goal in the league, which is a remarkable run.
Alejandro Garnacho brings a save out of Brentford goalkeeper Mark Flekken with a fierce drive. United have been turning the screw and have a corner.
