Moyes in a hurry to add to West Ham squad
West Ham sit 17th in the Premier League, a point above the relegation zone, after winning two out of nine league games since Moyes' appointment as Slaven Bilic's successor.
The club failed to complete a deadline-day deal for Sporting CP's Portugal international William Carvalho and the Scot believes midfield is an area West Ham must strengthen.
"I've given players opportunities," he told told the West Ham's official website.
"I'm in a hurry and I have to be in a hurry and because of that I cannot wait three or four months to see how you do.
"Ideally, I'd have had six or seven pre-season games to understand what they're like and what they do, but I've not.
"I've got to say every player has shown great desire and is committed in training, but I think we're short in some areas and overloaded in others. For example, we've got lots of forwards, but we're really short of midfield players.
"We've got quite a few who are comfortable playing on the left, but not so many who can play on the right, so we've got a little bit of an imbalanced squad which we've got to straighten out in January if we can."
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Defensive improvements may also be on the agenda for Moyes, whose side have conceded three goals in back-to-back league games against Newcastle United and Bournemouth.
"Obviously the last two games have been disappointing as far as goals conceded are concerned, whereas the three previous games it looked as if we had struck on something and become harder to beat," Moyes added.
"We've got a couple of forwards in form at the minute and people we can bring on and use, so I think we've got a threat, but we're definitely lacking in some areas of giving ourselves a chance of playing much better."