Better question: Who is Mastroianni and where did this come from?
The Twins have searched for versatile fourth outfielders for years, trying Jason Repko, Clete Thomas and Erik Komatsu in recent seasons, to name a few.
Mastroianni, who will turn 27 later this month, had all of two MLB at bats in his career before the Twins grabbed him off the scrap heap from the Blue Jays this past offseason, put him in the minors and watched him rise.
His minor league numbers don't suggest the same pop he has shown here -- his highest total in any minor league season is four homers, and he already has three here -- but he always stole a ton of bases and had a knack for getting on base.
He can play every outfield position, and he is even functional at second base. Mastroianni might be the kind of player ideally suited for the role he is in -- extra outfielder, pinch runner -- instead of as an every day player, where his flaws might show up more over the course of time.
Then again, with what he has shown even in semi-regular playing time, we can' t help but wonder what he could do with just a little more time on the field.