21-year-old Safuwan was impressive in Tuesday's opening league game against Kelantan, which saw the LIONSXII fall to a 2-1 defeat to the defending champions.
The composed defender formed an excellent partnership with Baihakki Khaizan, and negated the influence of Kelantan strikers Muhammad Gaddar and Norshahrul Idlan Talaha for much of the game.
However, Safuwan picked up a knock in the second half of that match, and while he was able to complete the game, it has now been confirmed he injured the lateral collateral ligament on his left knee, and will sit out Saturday's trip to Kedah.
Nonetheless, the LIONSXII are said to be confident the youngster will return in time for their next home game against Kuala Lumpur on Tuesday.
Kedah are not without injury problems of their own, after they confirmed talismanic forward Baddrol Bakhtiar will be out for up to a month with a hamstring injury.
Baddrol, who was awarded the Kedah captaincy after declining several offers to move to Indonesia in the off-season, picked up a knock in their last friendly against Perlis, and failed to take to the field in Tuesday's 3-0 loss to T-Team.
With the 23-year-old ruled out, Kedah will have to rely on Brazilian import Daniel Baroni and Malaysia international Khyril Muhymeen for goals.