Grimsby have brought a premature end to the loan spells of Derby midfielder Arnaud Mendy and Cardiff striker Josh Megginis.
Both players joined the Mariners on one-month deals recently but have been sent back to their respective clubs early.
The League Two club have cited a lack of first-team opportunities as the reason behind the decision.
"It's not for anything they have done in a bad way, it's just to be fair to them," Grimsby caretaker boss Neil Woods told the club's official website.
"I think I need to be fair to the players that we've got here first.
"They've been a little bit of a victim of circumstances in the last two weeks.
"They are not going to get into the 18 and I don't think it's fair to keep them here. They both understand the situation."