Perhaps you remember Nate Field, a relief pitcher who threw nine innings across 14 games for the Colorado Rockies back in 2006. Field, who spent that entire season in Triple-A, came up in September and made all those appearances after roster expansion, racking up 14 strikeouts across those nine frames, with a win, a loss, a blown save, and four holds.
Field, who was 30 at the time, used his '06 September call-up as a springboard to a gig in 2007 in the (then Florida) Marlins' organization, though he spent the year at Triple-A again, and only made one appearance in the Major Leagues.
I think of Field today because he's a (kind of random) comp to Simon Castro. After bouncing around the minor leagues between the Padres and White Sox organizations, Castro came to the Rockies in 2015, and spent the entire season in Triple-A Albuquerque. Castro's numbers were solid for the Isotopes -- especially relative to his home park and league -- with 74 strikeouts across 57 innings, a .242 opponents' batting average, and a 3.79 ERA in 36 games.
By September, Castro was called up to Denver, where he did in 2015 what Field did in 2006: immediately become a key part of the bullpen (on a non-contending team) for the final month of the season. Castro's big league numbers in 2015 didn't quite reach Field's in '06, but they weren't as bad as they look on paper, either: in 11 games (10.1 IP), Castro recorded a 3.13 FIP with 9.6 hits per nine innings and nearly a 2:1 strikeout to walk ratio.
Take away one bad outing on September 9 in San Diego (I know, I know) and Castro would've allowed just four runs on seven hits in 10.1 innings. He also showed confidence in two pitches -- including an 83.5 mph curve ball -- with unique mechanics and arm action that creates good fastball movement.
And although he declared free agency (nine years and two days after Field declared free agency after his stint with the Rockies), Castro did set himself up for some kind of opportunity in 2016 with a decent audition this summer.
Castro's 2016 outlook
Castro would've been an interesting depth piece to keep around the 'pen in 2016, but alas, he'll test the open market and see what's out there. Unlike Field in 2006, Castro is just 27 years old this winter, so he'll get a few more options than what Field found after his September stint in Denver.
I suppose there's a chance Simon Castro re-signs with the Rockies; he had a good experience in Albuquerque this summer, and Colorado gave him the longest look at the big leagues he's ever had (he appeared in four games for the White Sox in 2013).
Whatever the case may be, Castro is a great buy-low option for 2016. For a team that wants to take a flyer on a guy who at worst will be bullpen depth for a Triple-A affiliate, and at best will get a look as a middle reliever, I'd imagine there's a pretty good situation for Castro somewhere next season. And if he picks the right opportunity, he may find himself spending quite a bit of time in the Major Leagues.