Outlooks for top September call-ups

Nick Castellanos has moved positions often in Detroit's system, but the bat has been consistent. Mark Cunningham/MLB Photos/Getty Images

This year's roster expansion call-ups already have included a number of top prospects, with a few more likely to come up once minor league playoffs end in the next two weeks.

Here's a look at the short- and long-term outlooks for some of the biggest names who have come up so far, as well as the biggest name whom I expect to see later this month.

Taijuan Walker, RHP, Seattle: