Gregory unlikely to feature at The HiveMillwall look set to be without Lee Gregory for Tuesday night's EFL Cup tie away to Barnet (8pm).
The striker opened the scoring for The Lions in Saturday's game against Oldham at The Den but was taking off at half-time and is unlikely to be risked against the League Two side.
Byron Webster also took a knock against The Latics and will be assessed leading into Millwall's first-ever visit to The Hive.
Neil Harris has hinted that he will make changes to his starting line-up against Martin Allen's men, which could mean a full debut for Gregg Wylde as well as potential starts for the likes of Joe Martin, Jimmy Abdou and Fred Onyedinma. Shaun Cummings remains absent, though.
Barnet could hand starts to summer signings Jean-Louis Akpa Akpro and Jamal Campbell-Ryce, who both came off the bench in their 1-1 draw with Cambridge United on Saturday.
Another fellow new recruit, Alex Nicholls, struck The Bees' equaliser at the weekend and could well make his full debut against The Lions.
Gavin Hoyte and Jamie Stephens are still recovering from long-term injuries so won't be involved.
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