David Phelps's conventional and unconventional bullpen success

The Miami Marlins' bullpen has been in flux for much of the 2016 season. As of Wednesday, the Marlins had the 11th-best park-adjusted ERA and 17th-best park-adjusted FIP, and the reason why the Fish are more in the middle than towards the bottom is because of the team's balancing forces at the back of the pen. On one side, their destabilized seventh-inning pieces have been difficult to manage. The club has gone through Craig Breslow, Dustin McGowan (who returned in place of the DFA'd Breslow), Chris Narveson, Nick Wittgren, Jose Urena, Nefi Ogando, and Edwin Jackson among the several folks to handle middle relief duties for the team. On the other hand, David Phelps, Kyle Barraclough, and closer A.J. Ramos have served as a counterbalance to the instability at the front end.

Phelps, in particular, has been a revelation. Spending most of last season as a starter thanks to a myriad of injuries, Phelps was among the team's best starters, but he was not a good starter overall, especially toward the end before his injury. This year, he was started off in the bullpen and has excelled; his 1.71 ERA and 2.09 FIP look legitimate, and he is doing this with above-average strikeout rates beyond his career norms.

Phelps has done this with some interesting changes in his game. One of those changes makes lots of sense, while the other is a less traditional route to success.

Fastball Velocity

The most simple reason for seeing change and success in Phelps's game is his fastball velocity. With his permanent move to the bullpen, we are seeing an increase in velocity of his arsenal.

That is an increase of two mph when most pitchers are throwing slightly slower than they would be expected to toss. Such a velocity increase is significant in a pitcher and could help explain why his performance is so improved. The research has estimated a 0.3-run ERA improvement for every increase in one mph of velocity. Such a change would drop Phelps's expected ERA by 0.75 runs.

The numbers bear this out in terms of missing bats. The whiff rate for his four-seam fastball has gone up from 13 percent last year to 29 percent this year, more than double its previous. This is likely playing a big role in his performance increase.

This seems like a natural consequence of moving from starting to the bullpen. Most players moving to the pen gain velocity in the move, mostly because they can go all-out for a short burst of time rather than having to save themselves for longer innings.

Zone-Pounding

If it were that simple, it may not be worth investing the time to tell you about this change. However, there is something else that Phelps is doing that is very interesting.

Since coming to Miami, Phelps has really adopted the zone-pounding approach of the Marlins. He has thrown the ball a ton in the strike zone, but hitters are not offering on pitches outside the zone, meaning that Phelps still isn't fooling anyone with good breaking offerings. However, his contact rate is down a significant amount compared to before, the lowest he has ever posted.

We talked about his velocity going up and likely playing a role in his increased whiffs. However, those whiffs are often occurring in the strike zone rather than out of it. His in-zone contact rate is at 79 percent, something he has never achieved before. In comparison, his career rate is at nearly 90 percent.

Part of that is definitely the fastball increase, but with his contact rates out of the strike zone not being much different from his career marks, you have to wonder if the whiffs in the zone can continue. Relievers are better able to miss bats both in an out of the zone, but even at nearly 94 mph, Phelps is not some high-velocity burner. Of the relievers with the lowest in-zone contact rates in baseball since 2013, about half threw at his new velocity or lower and achieved those rates. However, they also had strong out-of-zone whiff rates suggestive of a pitcher with strong secondary stuff as well; none had a contact rate on out-of-zone pitches greater than 65 percent. In fact, Phelps's career 73 percent rate would have ranked among the ten highest out-of-zone contact rates among relievers.

There was a similar pitcher who had an increase in velocity and high rates of pitches in the strike zone. A few years ago, Nathan Eovaldi started the 2014 season with a high rate of strikeouts in the first month of the year. He put up a surprising 23 percent strikeout rate as a starter and had a velocity increase noted as well. He did it primarily by getting more foul balls and staying the zone, but eventually those strikeout gains declined and he needed to go to another team and learn a new pitch before he could regain a strikeout edge.

Is Phelps running into the same problem? On the promising side is that Phelps is still actually missing bats, which is something Eovaldi that season still was not doing despite the increased fastball velocity. Still, the disparity between the missed pitches in and out of the zone has me a little worried that we need more time with the new reliever Phelps before we can say he has definitely changed. Still, the signs still point towards improvement, and at this point the Marlins need Phelps to help stabilize the back of the pen.