McCann missed the 2-1 defeat by Stoke with a knee injury while Wallace limped off early in the second half.
Laws told the Lancashire Telegraph: "At the moment we're just investigating and Chris is getting treatment. Hopefully he'll get through this next week but we'll wait and see on that.
"As the weeks go by I think everyone gets concerned with it - the club as a whole - because we want to make sure we've got a good quality player on the park and it's frustrating when you haven't because we know he's going to be one of the major players in our team.
"Ross Wallace had a kick on the ankle, we're hoping that he should be okay. It was a precaution in bringing him off."