Doc, can you break down the bold a bit more? Taken to one extreme that would mean athletes can never take a rest day.
rest is different than immobilizing a limb and doing nothing with it.
here's where I get that statement... if you were in a hospital bed and did nothing but lay there all day, the amount of atrophy of your muscles, cardiovascular system, and body in general... for every day it takes you a week to get that back.
so, applying that to this scenario, the numbers don't translate 100% because Marcus isn't in a coma or a body cast. however, it's a good place to start as his lower leg will be completely immobilized until weight bearing in a boot can begin. the amount of tightness and weakness that will come with that is incredible. not to mention the amount of cardiovascular deconditioning that he will undoubtedly suffer.
I wouldn't be surprised if he has a very mild antalgia (limp) of some sort in his running mechanics come training camp. you'd hope they'd work that out, but a trained eye might be able to see it.
yes, he is more motivated than average joe. yes his job is to be in shape. yes, guys have come back in season after a broken fibula (see Randall Cobb... but he hasn't been the same player since to be honest). I'm just pointing out that the season starts in 9 months... and he'll be lucky to be running, cutting (at full speed) in half that time depending on how bad the break is. jumping, squatting/weight lifting is a completely different timeline...
then when you factor it takes 4-6 weeks after starting a lifting/conditioning program to start to see changes at the muscular level (strength changes during those first 1-2 months are primarily neurological level)... then maybe you can see why I'm skeptical.
I think eventually he will return to his original form in some way, but I would bet his scrambling ability will suffer at least next season. I really don't think this is a career ender in terms of he will be so bad he will go the route of RGIII, but it will change his career that's for sure. and next year will be a big questionmark. I hope they don't rush him back... if his strength isn't equal I'd be very concerned about a predisposition to an ACL or other ligamentous tear. that's the big risk of not fully strengthening after a bad injury like this... returning to full activity can run a huge risk of an ACL tear.