Watford manager Walter Mazzarri believes his side's poor start to their away match against West Ham was down to playing at the London Stadium.
The Hornets made a dramatic recovery in Saturday's match, going from 2-0 down to beat the hosts 4-2.
Before the victory, Watford had suffered three straight defeats and their fourth Premier League match of the season looked as if it would go the same way.
However Mazzarri argued once his players started playing their own football, then a win became possible.
Speaking through a translator, the Italian manager said: "We didn't start very well, mainly on the defensive part because West Ham had almost all of the stadium for them.
"They started very heavy and in a positive way. Unfortunately, it was hard for us at the beginning but then we started playing our football and the result came our way.
"It's extremely important for our confidence as a team. It will allow us to have a very good tournament."
It was a brilliant strike by France international Etienne Capoue that put the away side ahead just eight minutes into the second half, followed up by a fourth goal from Jose Holebas in the 63rd minute, sealing West Ham's fate.
Until Mazzarri was appointed as manager in July, Capoue had failed to score for his team.
However the 28-year-old has since achieved two goals in four league games and Mazzarri admitted he had been working with the midfielder in order to turn him into a goal scorer.
He said: "We worked a lot on Capoue. He's a very valuable player for us and he's given us results. But the reason he is scoring is because the whole group is playing in a very good way."