Little may be ruled out for the remaining four matches of the season after suffering a hamstring strain towards the end of the first half of Posh's 3-2 victory over promotion-chasing Watford at London Road on Saturday.
The right wing-back will undergo a scan to determine the full extent of the damage but manager Darren Ferguson is preparing himself for the worst.
"It doesn't look good for Mark, which is a shame as he's had a really good season," said Ferguson.
Michael Bostwick remains unavailable and his season could also be over after suffering a setback last week in his recovery from a hamstring injury, while fellow midfielder Jack Payne (ankle) will continue to be assessed.
Peterborough's run of nine matches without defeat is the longest current unbeaten streak in the Championship.
If Posh avoid defeat on Tuesday night, it will be the club's longest run without a loss at this level since the 1992-1993 season.