Wrexham keeper Andy Dibble will be out for three months after severing tendons in his finger in Saturday's draw with Tranmere.
"It cost us last year when Andy was out, he's a big influence on the club," said Dragons boss Denis Smith.
An error by stand-in keeper Matt Baker led to Sheffield United's winner in Tuesday's Carling Cup encounter.
"Matt will be a good keeper but has to learn from these things," Smith told BBC Sport Wales after the 3-2 defeat.
"It was just a comedy goal that shouldn't be seen at any level of football.
"I'm not quite sure what Matt was doing, but I have two centre-backs and a goalkeeper missing so there is a lack of understanding.
"Matt won't want to be remembered for that, and he's strong enough to come back."
Smith was also disappointed at the lack of finishing power shown by his side against the Blades.
"We could have been in double figures by full time," he said. "We're great at making chances but have to start finishing them.
"To say I'm disappointed with that defeat would be an understatement."