There's much more to hitting ability than just BA. Goodwin hit much better last season than Span. He did it in AA of course but you can't say he didn't hit well last year if you think Span did.
This post is actually about Zach Walters.
Goodwin was a .250 hitter in AA. Span hit .275 or so in the Majors. That's a big difference. I'd expect a player to hit better in AA, where more pitchers just throw fastballs. Espinosa hit .265, more or less, in the minors. Goodwin was also hitting in smaller parks and against weaker fielders. Re AA fielding: I every time I've been to Harrisburg, I've seen grounders to the left side and thought, OK, that's an out. Comes from watching Ryan Zimmerman and David Wright too much. In all cases, the Harrisburg 3B moved a couple steps and watched the ball roll into LF.
Example: take a guy who hit .265 in AA with 23 homers. In lower A he hit about .340. I would not start him over a guy who only hit 2 homers but hit about .290 in the majors. I'm cheating a little, since the first player is Dan Dobbek, and I had his Topps "rookie star to watch" card in 1959 or 1960. He was supposed to be the next Bob Allison. He played parts of three major league seasons, mostly hitting about .230 or less. The other is Lennie Green, a key player in CF for the 1960 Senators and then for the Twins.
Putting it another way, I'd rather have Mickey Rivers, Lennie Green, Bret Gardner, or Denard Span in CF, than a prospect who has not shown he can hit. When Goodwin hits in AA and AAA, then he'll be ready.