Colchester manager Tony Humes says his side cannot bring in another defender, despite having the worst defensive record in the Football League.
Saturday's 5-0 defeat at Wigan saw the U's let in their 27th goal, two more than next worst Morecambe.
"I don't think we can (sign a defender). We've got a budget, we know where we are in terms of that," Humes told BBC Essex.
"If you're missing three or four through injury, you can't do anything."
Defenders Richard Brindley, Alex Wynter, Jamie Harney, Kane Vincent-Young, Frankie Kent and George Elokobi have been carrying injuries for Colchester.
|Football League's worst defences (goals conceded)|
|Dagenham & Redbridge: 24|
After winning four straight League One matches, Humes's side have lost their last three games and lie 16th in League One, four points above the relegation zone.
But Humes paid credit to Wigan, after Northern Ireland international Will Grigg and defender Donervon Daniels both scored twice.
"Sometimes you just have to hold your hands up and say Wigan are a good team," said Humes.
"They were powerful, moved the ball quickly and we just couldn't cope with it all game.
"They've got international players in there, and it's clicked for them, they've probably been waiting for that all season."