Most players got issues with knees....some worst than others. If you can suit and still get there I wouldn't be too concerned. If he does nothing on the field for more than a few days I would begin to start thinking of the possibilities of further absences down the road.
TC is where you want to be the most cautious...no need risking a problem when its just practice....where talking about practice! LOL
I believe if it was during the season he would be a full go!