Millwall winger Chris Hackett could be set for a short spell on the sidelines after being withdrawn during the 1-1 friendly draw at Crawley.
Hackett was forced off with a back problem before the end of the first half against the Conference club.
Jackett told the club's official website: "Chris has struggled with his back to be honest, but he wanted to play. I didn't think he looked quite right, so we took him off quite early.
"His back may keep him out for the next four or five days of training, but I don't anticipate a problem beyond that."