James Tomkins admitted Saturday's performance against Southampton was one to forget after West Ham United failed to build on last weekend's win over Crystal Palace.
Mark Noble fired the Hammers into a first half lead on their return to the Boleyn Ground, but a Morgan Schneiderlin double and Graziano Pelle's late goal consigned them to defeat.
Tomkins was especially annoyed to concede two goals from set pieces and he says the Londoners will have to work hard on the training pitch to ensure it does not happen again.
"The only positive from the game is Nobes' goal," he admitted. "We never really got going and didn't deserve to win on Saturday.
"We should have gone on from our goal. They had a lot of possession, but I didn't think they were going to score, but then they've got one from a set play which was frustrating from our point of view.
"We work hard on them, so to let in another one in the second half is very disappointing. We're going to have pick ourselves up, because we've got two weeks to get it right for the next game.
"To go from such a high last Saturday and go into today's game with such confidence, we felt we could win the game, but maybe we thought it would be easier than it was and they played really well.
"We wanted to go into the international break with a positive and it hasn't worked out that way. We'll be disappointed for the next couple of days, but we can't lie on that and we'll have the chance to work on what we did wrong on Saturday."
The Hammers completed their eighth summer signing on the day of the game, loaning Alex Song from Barcelona for the season, and Tomkins is looking forward to working with the midfielder.
"Alex comes with a great record, playing for Arsenal and Barcelona," he added. "It's a good signing and it shows what the club's trying to do here.
"Hopefully he can settle in quickly."