Andy Whing: Oxford United defender out until mid-January
Oxford United midfielder Andy Whing faces at least two months on the sidelines with a groin injury.
U's manager Chris Wilder confirmed that it is a recurrence of the problem which has already hampered the 29-year-old this term.
If Whing sits out the next eight weeks he will miss 11 League Two matches.
"He's out well into the new year, possibly mid-January. We've now lost a number of important players," Wilder told BBC Radio Oxford.
"It feels like we've been here before with all these injuries."
Deane Smalley (groin) was also injured against the Stags, with Whing joining Jake Wright (hamstring), Jon Meades and Alfie Potter (both ankle) on the long-term injury list.
Oxford defender Michael Raynes said the loss of Whing could harm the League Two leaders' promotion hopes.
"We are gutted for Whingy, and it is a massive blow for us," Raynes said.
"There are not too many people in the Football League that can do the job that Whingy does. Everyone needs a player like Andy Whing in their team.
"But we have good young lads that can now come up, who need to put their hands up. Josh Ruffels has been outstanding in training so he will get an opportunity now to make a mark."