Navarro got to the majors as a 22-year-old and played for the Boston Red Sox and Royals last season. He has good power for an infielder, but his defense is suspect, particularly at shortstop. He's played shortstop, second, third, and all three outfield positions in the minors. The Pirates are probably figuring that Pounders and Goris aren't much to give up for a young major leaguer, so they'll take a look at Navarro in Spring Training and see if they can carve out a role for him as a bench player.
Pounders was a second-round draft pick in 2009. He pitched well in relief for Class A West Virginia this season, but the fact that he was pitching in relief less than two years after being drafted in the second round doesn't really bode well for him (and it demonstrates the pitching depth the Pirates had at Class A). Goris played all the way down in the Dominican Summer League last year; his stats were good, but he was playing against younger competition, and it's impossible to take DSL stats seriously. I've never heard him described as a top prospect, but maybe the Royals' scouts see something in him they like.
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