Since 2002, 620 different major-league pitchers have thrown at least three hundred innings. With the signing yesterday of Tyler Clippard, the Diamondbacks' bullpen will include both the man over that time who has generated the lowest percentage of fly-balls (Brad Ziegler,. 16.1%) and the man who has generated the highest percentage of fly-balls (Clippard, 56.6%). We know what Ziegler has done, but there's some concern over the new arrival, particularly given the hitter-friendly nature of Chase Field. Is that warranted?
Generally, ground-ball pitchers will give up more hits and have that higher BABIP, but those hits will tend, as we have seen with Ziegler over his time with Arizona, to be singles. Fly-ball pitchers generate more outs (Avg on fly-balls is lower then ground-balls, .207 vs. 239) but they are likely to go for extra-bases - or, obviously, leave the park entirely. To a large degree, these cancel out and there isn't any clear answer to the question of whether a ground-ball pitcher is "better" than a fly-ball pitcher. Fangraphs looked at the issue in December 2014, and concluded, "One type isn’t better than the other, they’re just different. You can be good, bad, and in between no matter your rates."
However, the problem with trying to predict what Clippard might do, is that we haven't had anyone like him at all pitch for the team. Even if we drop the innings limit to 200, over the period for which we have reliable figures (since 2002), it seems we have not had a pitcher that generated fly-balls at any more than a 50% rate. So this is severely uncharted territory for any D-backs pitcher. Still, to see if we can get some idea of what to expect, here are a selection of statistics for the six most fly-ball inclined pitchers (min: 200 IP), as well as the career figures for Clippard.
Just to explain the stats that might not be obvious: LD% is line-drive percentage; HR/FB is the percentage of fly-balls that become home-runs; FIP is fielding-independent ERA; xFIP is FIP adjusted for a "normal" HR/FB rate; and the last three columns are the percentage of balls in play that were "hit with a certain amount of authority".
One of the things which certainly helps explains Clippard's success is that low line-drive rate: MLB average last season was 20.9%. If fly-balls and ground-balls are just slightly different flavors of outcome, line-drives are a poison pill, with an average on them of .685. At the risk of stating the bleedin' obvious, pitchers that give up a lot of those, will not find success. Clippard's avoidance of line drives is also reflected in a higher percentage (22.3%) of softly-hit balls against Clippard: the average figure in 2015 was 18.6%, and even that was above what it has generally been lately.
He has also been better than normal at keeping the ball in the park: while HR/FB does vary (last year it was 11.4%, the one before only 9.5%), it has always been higher than Clippard's 8.2%. [Worth noting, Chase Field doesn't seem to impact that figure much. From 2002-15, our median HR/FB% was 11.2%, compared to 10.6% across all MLB].Again, this figure may be influenced by Clippard's ability to avoid hard-hit balls: it doesn't matter how many fly-balls you give up, if they are hit weakly enough to drop into the gloves of waiting outfielders. Although, if you allow a lot of hard hits and fly-balls... You become Yusmeiro Petit, with a brutal HR/FB rate, and ERA north of five.
As you can see, there really isn't anyone in team history whose profile can be said to be a good match for Clippard. In terms of HR/FB and Soft%, his closest parallel would appear to be Josh Collmenter, though Colly gives up a lot more line drives than Clippard ever has. If Clippard can continue his previous tendencies, there's likely no reason he shouldn't be able to continue his previous success. As ever, however, the key word there is "if", and past performance is no guarantee of future success. Still, he only turns 31 next week, and I'm cautiously optimistic that, health willing, this contract will turn out to be a decent one for the Diamondbacks.