I won't say this is a good thing, but there's one huge upside; Messi now gets a rest. He had been looking a little tired lately and the resounding the factor of last year was fitness is above all else, especially when the talent is there. I assuming he won't go play any of the 4 international games either which is no harm. We've had our toughest CL game played and didn't get beaten. This period will also show us if Munir is worth a wank. He'll be itching to play when the Clasico roles 'round too.
He has a knee ligament damage. He might not be playing, but he's hardly getting any rest tbh. It's better for him to play and not rest than have this injury.
In terms of fatigue down the line ? No. 7 weeks of professional football is more draining than recovering from a knee injury is. Problem is, while most of Messi will be fresh & ready, he'll probably be very careful with what he does on the pitch, hurting his gameplay a little.
Fatigue wise Messi should be in great shape for the 2nd half of the season.