Tottenham manager Mauricio Pochettino admitted that his side were not up to scratch as they slumped to a 1-0 loss to West Ham at Upton Park on Wednesday.
Michail Antonio's header from a Dimitri Payet corner put the Hammers ahead as early as the seventh minute, with Spurs unable to muster a response as they slip three points behind Leicester City in the title race.
"We made some mistakes in the first half and we're disappointed about that because it was difficult for us to be in the game and difficult for us to play the way we want to play," Pochettino said.
"I thought we played better in the second half, managed the game better and created chances but if you don't score, it's difficult to take anything positive out of the game.
"We were poor in the first half and that's why we all feel disappointed. It's also true that we needed to be better from the beginning as we also conceded an early goal against Swansea. That is something we need to improve and change in the next games."
Next up for Spurs is the north London derby against Arsenal at White Hart Lane, when the Argentine coach will be determined to have his players back to their best.
"It's important now to focus on the next game," he added. "We need to be ready for another derby and to make sure we arrive in the best condition on Saturday."