West Ham co-owner David Sullivan believes a number of the club's foreign players "couldn't be bothered" because they expected to leave Upton Park before the close of the transfer window.
West Ham currently sit bottom of the Premier League having lost all three of their opening games and, with a difficult run of fixtures coming up, they could find themselves even further adrift by the end of the month.
Sullivan, though, believes the Hammers will improve as he expects the unnamed players to up their game having failed to secure a move away.
"We've got a few foreign players who wanted to leave but we didn't receive any offers," he told the News of the World. "I think they couldn't be bothered but now the deadline has passed they realise the only way out is to play for the club and to play well and I think they will make a contribution.
"They are here until at least January so they will get their heads down and work for the benefit of the club. They had their heads in the air before that.
"The team that started against Manchester United was the same team from last season because virtually all the new signings were injured. Out of our new signings, Victor Obinna didn't have international clearance, Thomas Hitzlsperger was injured, Winston Reid has a torn muscle in his buttocks, Tal Ben Haim was not fully fit and Pablo Barrera was knackered after playing two full games in the week after the World Cup.
"Now, with our new players getting back and the others back playing, you will see us get better game by game. The next three games are very, very tough - Chelsea at home; Stoke, who are particularly good on their own ground; and Tottenham at home.
"Three tough games and then the season really starts with the Fulham game on October 2. The Bolton game was a major disappointment but it's early days."
The News of the World reports that Avram Grant could be dismissed shortly if the Hammers fail to move up the table, but Sullivan told the paper: "I haven't relayed any messages to Avram at all. I just expect a gradual improvement in form.
"He'd love to have £30 million to £40 million to spend, but what manager wouldn't? He inherited a very imbalanced squad and it's significant."