See what happens when you let him play? The key for Marcus now, I think, is to stay healthy. Second base is, next to catcher, the most physically taxing position on the field. Marcus has had injuries each of the last two seasons, but both were fluky one-time injuries and shouldn’t have long-term impact. His Joe Morgan-type build gives him as good of a chance as anyone to survive at second base for the next few years.
He doesn’t have to get any better to be a star, not after putting up the numbers he did last year — he just has to maintain that production. But he could improve. He had 49 doubles, 21 homers last year, and over the next couple of years some of those doubles might turn into homers.
His defense improved to where it actually benefitted the team rather than just not hurting it. He was good on the double play and (for what it’s worth) led qualifying NL second basemen in zone rating… Comparable hitters through age 25 include Mike Sweeney, Bret Boone, Ken Boyer, Jim Gilliam, Jose Vidro, and Jeff Kent. Kent isn’t really comparable but I think he’s actually the best fit.