Mauricio Pochettino watched his Chelsea side get beaten 2-1 by a struggling Manchester United side on Wednesday night.
It was a major setback for the Blues, who were hoping to build on their hard-fought 3-2 win over Brighton just this past Sunday.
Scott McTominay put the hosts ahead after 19 minutes, before Cole Palmer brought Chelsea level just before half-time.
The Scotland international then made it 2-1 with 21 minutes remaining on the clock after fighting off a challenge from Levi Colwill to get on the end of a Alejandro Garnacho Cross.
United could have scored more, to be fair, especially in the first half when they created too many chances, but the same can be said of Chelsea, who were presented with at least three very good opportunities to even snatch the victory.
Pochettino later told Amazon Prime Sport: “We cannot put it all on Cole Palmer’s shoulders because he is really young. He came on the last day of the market to help us. It was a good goal.
“We created enough chances to be in the game. We started the second half really well but then we concede and it is difficult.
“We need to be more clinical in places like Old Trafford. We conceded the second goal and it was more difficult. We need to make better decisions. It’s hard with all of the emotion out there.”