Jeremy Horst was acquired for Wilson Valdez during the 2011-2012 offseason. Well, that worked out pretty well.
2012 Season: 1.15 ERA, 31.1 IP, 28 H, 14 BB, 40 K
ZiPS 2013: 4.41 ERA, 65.1 IP, 29 BB, 54 K
Bill James 2013: 3.94 ERA, 48 IP, 21 BB, 43 K
Steamer 2013: 3.85 ERA, 30 IP, 13 BB, 26 K
Oliver 2013: 3.52 ERA, 72 IP, 28 BB, 59 K
This will, hopefully, be the last time I mention Wilson Valdez in an article, and it feels a little unfair to mention him in Horst's preview as he had a damned fine season without mention of Exxon. It's worth noting that in half a season, Horst has matched Valdez's career WAR at 0.6 fWAR. It's also worth nothing that Horst had some luck in his side last year. For example, a 3.7 HR/FB is remarkably low and bound for some regression, as most players usually hover closer to 10%. Of course, some players seem to be able to manage this and maintain relatively low rates. Matt Cain, for example, has never even gotten very close to a 10% rate. That said, Cain's average rate is still well above 6%, so It seems crazy to think Horst won't regress here.
Most of the rest of his stats were around his minor league career norms, except his K rate which was ~3 K/9 higher last year. Perhaps that can be maintained, but it's much more likely that will regress as well to something closer to 8 K/9. That is manageable if his BB rate can stay down.
Horst is not solely a LOOGY, which is nice. His splits are pretty even (including his minor league splits, though even including those Small Sample Size issues abound). Horst was a pleasant surprise last year, and while I don't expect he'll repeat it, I also doubt he'll be bad enough to not be with the club for a significant portion of the year. That said, The Phillies have enough pitching depth they've been giving some away for free, so it's certainly not a done deal that Horst spends the year in Philly either. He's got competition from Diekman, who's great when able to find the plate, Valdes, Savery (likely to stay in Lehigh most of the year), and it's not any kind of guarantee he'll beat them because of experience in the bigs, as they all spent time with the parent club last year too.