The Red Devils lost 4-0 to the Bees at the Gtech Community Stadium in their second Premier League match of the new season. Goals from Josh Dasilva, Mathias Jensen, Ben Mee, and Bryan Mbuemo sealed a fantastic victory for the hosts inside 35 minutes.
While Manchester United lacked cohesion throughout the 90 minutes, the individual mistakes cost them against Brentford. David de Gea was at fault for the first two goals, while Lisandro Martinez could have arguably done better to prevent the third.
The Red Devils have now lost both of their opening Premier League fixtures and sit at the bottom of the table for the first time since 1921. Previously, Ten Hag's side lost 2-1 against Brighton & Hove Albion at Old Trafford on the opening day of the Premier League last weekend.
After their loss against Brentford, Ten Hag admitted they needed to sign more players this summer. He said (via the Mirror):
"We need new players and quality players. We will try and convince them to join."
The Red Devils signed left-back Tyrell Malacia, midfielder Christian Eriksen, and defender Lisandro Martinez this summer.
Ten Hag's side will next face rivals Liverpool at Old Trafford on August 22. The Red Devils lost the fixture 5-0 last season.
Manchester United's transfer roundup
As per the aforementioned Mirror report, the Red Devils have been linked with several players this summer.
They are interested in signing Barcelona midfielder Frenkie de Jong and Juventus midfielder Adrien Rabiot to strengthen their weak midfield.
They lost Paul Pogba, Nemanja Matic, Jesse Lingard, and Juan Mata this summer after they all left on free transfers.
Meanwhile, Manchester United are also interested in signing Paris Saint-Germain forward Mauro Icardi (via TyC Sports). They will, however, have to compete with Galatasaray for his signature.
PSG manager Christophe Galtier has told the Argentine to find a new club this summer, and Icardi could leave on loan. He has registered 38 goals and 10 assists in 92 appearances for the Ligue 1 champions across all competitions.
With Edinson Cavani leaving this summer and Anthony Martial's injury issues, United could need to sign a striker to support 37-year-old Cristiano Ronaldo. The Portuguese's future at the club isn't clear either.
Incidentally, as per another report by the Mirror, PSG are interested in signing Marcus Rashford this summer. They have even held talks with the forward's agents, but Manchester United are unwilling to sell their academy graduate.