Michael Carrick said Manchester United were not clever enough after they let a 2-1 lead slip in a 3-2 loss at West Ham on Tuesday that serves as a devastating blow to their Champions League hopes.
Having fallen behind to an early Diafra Sakho strike in the final game at Upton Park, United turned things around through an Anthony Martial double.
But goals from Michail Antonio and Winston Reid ensured victory for West Ham in a result that leaves United two points behind Manchester City in the race for Champions League football and clinches Arsenal's place in Europe's premier club competition.
United must now beat AFC Bournemouth on the final day of the season on Sunday and hope Manuel Pellegrini's men suffer defeat at Swansea City
And Carrick told Sky Sports: "We were in a good position but we didn't help ourselves. You have got to be better than that, cleverer than that.
"The atmosphere was loud and what we expected before the game. We have been in big atmospheres before. You have got to deal with that.
"It is Man City's hands now [to finish in the top four]. We have let that slip. We have got to win our final game and see what happens."