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Preview, #128: 8/21 vs. Rockies

Yoan Lopez: bullpen savior or relief mirage?

Washington Nationals v Arizona Diamondbacks Photo by Christian Petersen/Getty Images

Today's Lineups

Raimel Tapia - LF Jarrod Dyson - CF
Trevor Story - SS Ketel Marte - 2B
Charlie Blackmon - RF Eduardo Escobar - 3B
Ryan McMahon - 3B David Peralta - LF
Yonder Alonso - 1B Jake Lamb - 1B
Garrett Hampson - 2B Josh Rojas - RF
Yonathan Daza - CF Nick Ahmed - SS
Dom Nunez - C Alex Avila - C
Tim Melville - RHP Mike Leake - RHP

Especially given a convoluted road to the majors, including multiple unscheduled departures from his farm team, on first glance, Yoan Lopez has had a pretty good rookie year. He has tossed almost fifty innings with an ERA of 2.66: the only D-backs rookie relievers to have done as well were Yoshihisa Hirano (as a 34-year-old!), Jose Valverde and Oscar Villarreal. On this basis, he looks set to be a solid part of the bullpen for years to come, and has been discussed as a potential future closer. But there are some worrying signs on Lopez’s peripherals, which suggest his sparkling ERA might, at least somewhat, be due to luck, and also be tough for him to sustain going forward.

For his fielding-independent ERA (FIP) is 4.81. That’s more than two runs higher: among the 341 pitchers with 40+ IP in the majors this year, only two have a larger gap. That’s worrying, because FIP tends to be more predictive of future performance than ERA. The main element of concern is Lopez’s K-rate: 6.2 per nine innings is basically the same as T.J, McFarland (6.1), and we all know of his struggles this season. Fewer K’s = more balls in play, which tends to mean more hits. Lopez has avoided this, due to a BABIP of .204, ninety-three points below major-league average, despite a normal line-drive rate (24% vs 25%). Meanwhile, McERA sits at a .344 BABIP. That’s basically the difference between their performances this year.

The low K-rate is a bit of a surprise, as Lopez fanned better than a hitter per inning (9.5) in the minor leagues. You can get away with this, if you have pinpoint control and rarely walk people. But at 2.27 per nine IP, Lopez has been good, rather than great, though this is actually better than his average in the minors (3.9). Succeeding as a reliever with a K-rate below 6.5 is tough. There are nine men in the majors like that, who have thrown 40+ innings this season. Never mind three, Lopez is the only one of them with an ERA below four. If he’s to enjoy sustained success in the bullpen, the odds are that Yoan will need to find out how to get those K’s back.