See above re: OPS and why it is not a good thing to compare them. I prefer OBP for middle infielders who do not hit. And it is not a prospect comparison, it is a ceiling comparison or who will serve the Twins better in the nearer future. Career numbers do not matter, because players click at some point. The fact is that Vielma had a higher OBP (.345, and above his league average .321) against more advanced competition in AA. Gordon has not yet reached AA. His best OBP was .335, achieved against lesser competition in high A. Whether Vielma or Gordon have higher ceiling with the bat is up for discussion, but Vielma can hit ok. Previous post. .750 OPS, 40 SB, above average glove at SS is about 2.5 fWAR. And that .750 is about .030 points higher than Gordon's best, btw. To Vielma a .265/.321/.338 .659 OPS, 5 SB, elite glove SS has 3.2 fWAR (Andrelton Simmons's 2015 numbers). I'd give a bit more to Vielma because of the SB (and Vielma's best OPS was higher than that). So if Vielma hits .270/.330/.350 (very doable for him) and steals 40 bases (career best 35 vs Gordon's 25) , he will be a 3.5fWAR player, about 1 point more valuable than Gordon.