Jack Flaherty's low walk rate has him in exclusive company (for now)


I wanted to write this post while I still have time.


Jack Flaherty is set to make his fifth start of the season this evening at home against the Brewers. His four previous starts can most easily be described as two very good starts and two not so good starts. Coming off a breakout year in 2018 in which Flaherty had a 3.34 ERA and struck out nearly 30 percent of batters in just over 150 innings pitched, he's allowed a lot of runners to score in the early going of 2019 as evidenced by a 5.00 ERA, which, unfortunately, has fit right in with the rest of the rotation.


Although his strikeout rate has dropped a bit, he's still striking out more than one in every four batters, and, most encouraging, he hasn't been walking many batters at all. Last season, Flaherty gave the free pass to 9.6 percent of batters, something you can easily live with when you're striking out 30 percent of them, and when it's not much worse than the league average (8.1 percent) for National League starters anyway. But so far this season that number for Flaherty has fallen to 4.9 percent - only four walks total. 


So he's striking out more than 25 percent of batters faced and walking fewer than five percent. It's early, of course, but of the 146 starting pitchers in MLB this season to have thrown at least ten innings, only six others (Blake Snell, Max Scherzer, Patrick Corbin, Hyun-Jin Ryu, Yonny Chirinos, Matt Moore) join Flaherty in this club. That number will thin out soon, maybe even by the time you're reading this, but if Flaherty can somehow maintain this pace, history shows that everything else will be fine.


Using Baseball Reference's Play Index, here is the list of pitchers who have thrown at least 150 innings in one season while striking out at least 25 percent and walking fewer than five percent:


A few takeaways. First, there's not a fraud on this list. The worst bWAR above belongs to Chris Sale in 2015 and he was nearly a three-and-a-half win player. Second, given the rising strikeout rates in baseball, it should come as a surprise to no one that exactly half of these seasons have occurred over the last five years. Third, let's be sure to admire 1999 and 2000 Pedro Martinez, probably the great run by any pitcher in the modern era. And finally, look at Sandy Koufax. On an island to himself for many years until he was finally joined by Pedro in 1999. 


That's a good, exclusive list. One I don't expect Flaherty to join, but I don't expect his ERA to stay around 5.00 either, and, more importantly, neither do the projections. And it's worth keeping an eye on whether he can keep that walk rate below league average. He's only walked 20 percent of batters who have reached a three-ball count against him - and that ranks in the 93 percentile for all starting pitchers in this very, very young season - so maybe that means he's been lucky? I dunno. But in a season when it's been tough to find something good to say about the starting rotation, the early returns on Flaherty's walk rate is at least something.