Manchester United manager Jose Mourinho admitted his side have to improve after they suffered their third defeat in eight days with a 3-1 loss at Watford on Sunday.
Substitute Juan Zuniga scored the vital goal with his second touch eight minutes from time and Troy Deeney put the icing on the cake with a last-minute penalty.
Watford, who claimed their first win over United in 30 years, moved into the top half of the table while United remained sixth, six points behind leaders Manchester City.
"I think in the first half for about 25, 30 minutes we didn't play well and that is something we can improve," United manager Mourinho said.
"The only thing we can control is our individual and collective mistakes. Our individual and collective performance is where we need to improve."
Odion Ighalo had already missed an open goal before Etienne Capoue put Watford in front after 34 minutes with a nice finish from the edge of the box.
Marcus Rashford equalized for United just after the hour mark after Zlatan Ibrahimovic's cross fell kindly to him one yard out.
Ibrahimovic then saw a powerful header well saved by Heurelho Gomes before Zuniga swept in the second with a superb finish and Deeney then finished things off from the spot.
"We were playing well, we conceded a goal and we stopped playing and we were afraid but then we made the changes and everything went the right way," Watford manager Walter Mazzarri said. "It is something we need to work on.
"We have been improving, I don't look too much on results but how we play and we have been improving dramatically."
Crystal Palace hammered Stoke City 4-1 to also move into the bottom half and send Mark Hughes' side to the bottom of the table.
James Tomkins, Scott Dann, James McArthur and Andros Townsend scored the goals as Stoke let in four goals for the third time in four Premier League matches.
And Southampton moved out of the bottom three thanks to a 1-0 win over Swansea, Charlie Austin scoring the vital goal.
Later on Sunday, Tottenham can go third if they beat Sunderland.