The England international limped off in the first half of last night’s 2-0 Serie A victory over Lazio.
Coach Stefano Pioli will only know the extent of the damage when he has the tests on Monday, but Sky Sport Italia are reporting sources within the club are confident he will not be ready for the Champions League encounter with Borussia Dortmund or next week’s Serie A fixture against Genoa.
Initial reports had said it was a groin issue, but these have been adjusted to suggest it is an abdominal strain that he sustained while twisting too quickly.
If confirmed, that would be a fairly unusual injury involving a few different muscle groups and require caution for a full recovery.
This is a problem for Milan, who are already missing Rade Krunic, Ismael Bennacer, Pierre Kalulu and Mattia Caldara.