Let's not say overwork--let's just look at what is "normal" for high-end backs. For starting work-horse RBs in the B1G, who have played in all 4 games, the highest number of carries (apart from Darius) are Nate Carter, MSU--73; Kyle Monagai, Rutgers--69 and Katron Allen, PSU--63. None of these three work-horse backs are freshmen. No other backs in the B1G have more than 50 carries in the first 4 games.
Now take Darius Taylor, who really didn't play in the Nebraska game (1 carry). He has had 86 carries in the past 3 games, far more than any other workhorse back in the B1G. And, therefore, far more physical punishment. And he is a true freshman. If nothing else, we all must agree that this is quite statistically "abnormal." Whether its is good abnormal or bad abnormal remains to be seen. But in general, good teams almost uniformly rotate RBs AND have a less lopsided run/pass split to preserve the health or utility of their RBs (who take a lot of punishment on every carry) for the long, drawn out season.
There are exceptions, of course, and maybe this season in the B1G Darius is one. Maybe running him play after play after play, when the box is staked, is just what the doctor ordered. Maybe abandoning the passing game to give him more touches once we have a lead is the winning strategy. I hope Darius is the true exception ... because this is, we all must admit, not normal even for work-horse backs.