First, there's reading the tea leaves on the timing. Why would they bring him up now, when everyone knows that Stan Kasten and Mike Rizzo can push back delay Storen's eligibility for arbitration by a year if they wait just a couple more weeks?
There are several factors. First and foremost, Storen really does seem ready to succeed. He's put up a 5.82 strikeout to walk rate over 53.2 minor league innings since last summer. Minor League Splits says he'd have a 3.95 ERA over that time if he was going up against major league pitchers. Scouts say he needs to work on holding runners, but he's not putting very many guys on in AAA anyway.
Adam Kilgore points out that the downside of Storen getting super-2 status isn't nearly what it is for Stephen Strasburg. Relief pitchers just don't get paid as much. Take a guy like Jonathan Broxton. He's clearly one of the top young closers in the game, and he had to "settle" for two years and $10.95 million in his first arb-eligible year. So even if Storen is as good as Broxton, you're really only talking about spending the equivalent of one Paul LoDuca signing for that extra year.
Chris Needham speculates that the team could indirectly help push Strasburg out of super-2 status by calling up Storen earlier. That's possible, and the team could do even more in that direction by bringing up Derek Norris and Bill Rhinehart right now.
There's also the fact that relievers are easier to bounce back and forth to the minors. If Stoen hits a rough patch in a month, it's not going to be terribly disruptive to work it out in Syracuse.
But here's one last cockamamie theory I haven't read anywhere: Stan called up Storen in order to stick it to Scott Boras. See, Kasten hates agents. And he hates the current draft system. He thinks that players who get drafted should have no rights to negotiate, and he really hates the signing period brinksmanship which leads many top players to wait till the last minute to sight.
Storen was the exception. He signed right away. Kasten says that players that don't sign right away (for what he wants to offer them) hurt their ability to get to the majors faster. This is his chance to say to Scott Boras, "see? if your players sign right away, we'll bring them up right away." Here's looking forward to the Bryce Harper-Drew Storen comparisons later this summer.
- Update: Re-reading my last bit of this post, I realize I really didn't make my point clearly. Really, I think Stan is thinking about negotiating with future picks, like Bryce Harper. By calling up Storen now, he has a new talking point for why Harper shouldn't wait till the last minute to sign. Expect him to say, "If Bryce wants to play, he should sign now. Look at Drew Storen. We will play Bryce as soon as he's ready, but if he doesn't sign, he's delaying his career."