The 22-year-old will come in to replace the injured Adam Chapman for the visit to Exeter City.
As it stands, Cox is into his final week at United on loan from rivals Swindon Town.
But if he did return to the Robins in January, it would leave the U’s desperately light in central midfield.
Chapman is not expected back until early February after damaging ankle ligaments last week, while the same problem is likely to keep Andy Whing out for several weeks.
With Jake Forster-Caskey looking likely to return to Brighton & Hove Albion when his loan expires, Wilder would be left with only Peter Leven and Simon Heslop as the only fit specialist central midfielders in the first-team squad.
The U’s boss was pleased to see Cox, who has made more than twice as many appearances for United as he has for Swindon, bounce back from a spell out of the side with a decent performance against Accrington Stanley last week.
He admitted the club were considering trying to extend the deal.
“It is a situation where we’re talking all the time to see what we’re doing in January,” Wilder said. “Lee could get recalled, but it is still in our minds as well that we might try to extend it.
“We’re just in the process of talking with the chairman of what direction we’re going in. We’re looking and weighing up the options.
“I thought Coxy did well last Tuesday. He had a little bit of a dip and found himself out of the team, but when he plays like that, gets about the park and breaks things up then he’s a good player.”
United have made one signing, bringing Josh Parker in on non-contract terms last Friday.
The 22-year-old striker was a free agent, so was able to join outside of the transfer window.
Some supporters questioned why a striker was needed when youth team graduate Tyrone Marsh was in the squad, but Wilder felt Parker’s background made him a better bet at this stage.
“Josh has played at a decent level with QPR and Oldham – he’s a young boy, but he’s not a teenager like Tyrone who hasn’t got any league experience,” he said.
“He will most certainly be involved in the 18 and who knows what will happen in the next two or three games, he might even start.
“We’re looking to see what he does to see if there’s anything going forward in January.”