IIRC, Pete Carroll himself said that Michael's preseason fumbles were freak occurrences. Michael did everything right on those two plays, but sometimes fumbles happen anyway.
His fumble against Arizona was the first regular season fumble of his career, basically it's too soon to judge if he has a fumble problem based on the sample size so far. Of course, he still needs to learn to transfer the ball better when running and he did have a fumble problem in college. Doesn't mean it can't be fixed.
I think sometimes as fans we focus on negative plays too much. For example, DeMarco Murray is one of the more fumble prone RBs in the NFL. Many of the top WRs in the NFL, including even Jerry Rice, were well known for having drop problems. Sometimes great defensive players and great offensive linemen rack up penalties. It's annoying but these drawbacks can be overcome with high caliber play.
Turbin is improving every year, and he just doesn't fumble. He is not easy to beat out on a team that is all about the ball. But, Pete is also all about the big play, and Michael has the ability to be one of the best big play RBs in the league. I think the competition between the two is probably very close, but Turbin gets the edge due to his extra year of experience and for the simple reason that he suits a #2 RB role better than Michael does.
Given how rare fumbles are and how little a #2 RB touches the football, I would think that pass protection is a much bigger factor than fumbles for the #2 RB job. And Turbin, though hardly perfect in protection, is definitely a cut above Michael at this point.
But what happens when Lynch is done and these guys are competing for new jobs? Given that Turbin doesn't really have a ton of rushing talent and Michael doesn't have a lot of pass pro ability, it seems unlikely to me that Turbin-Michael would be the 1-2 in the post Lynch Seahawks.
