Zack Greinke is currently leading the majors with a 1.58 ERA

Zack Greinke is off to another strong start, and he currently leads Major League Baseball with a minuscule 1.58 ERA. Will he be able to maintain this level of run prevention the rest of the way?

Before I dig into Greinke himself, let me lay the groundwork by taking a look at the defense behind him. The Dodgers are below average in rSB, which measures the pitcher’s contributions to preventing the running game while also giving credit to the catcher for doing his part in preventing stolen bases as well as throwing out runners. The Dodger defense behind him ranks slightly above average in total defensive runs saved. When looking at the total picture, the defense Los Angeles fields is slightly above average.

Now let me move on to Greinke’s numbers. Looking at his plate discipline statistics, nothing really sticks out as cause for excitement or concern. His swinging strike percentage this season (11%) lines up with his three-year average (11%) and are just slightly above his career numbers (9.5%). He has a slightly above average first-pitch strike rate (63.9%), which also lines up with his career numbers.

The batted ball profile for Greinke is much like his plate discipline snapshot in that nothing has deviated too far from his averages, except for one important area. His fly ball percentage of 33.4% is nearly five percent higher than last season (28.5%), but still below his career average of 35.7%. The one point to note is that while his fly ball percentage is up, his HR/FB rate is down to a low 7.1%, which is two percent lower than his career average (9.2%) and nearly three percent lower than league average. While not earth-shattering, a rise in fly ball rate coupled with a drop in home runs allowed implies a bit of luck and this is backed up by a low 0.58 HR/9 rate, which is better than his career 0.85 HR/9.

The final aspect of analyzing Greinke’s low ERA lies in his ultra-high 88.9% left on base percentage, compared to a league average 72%. While not all pitchers will regress towards this number (high strikeout pitchers tend to pitch their way out of jams), it’s important to identify if Greinke has been the beneficiary of luck. His career left on base percentage is 74.6% and his last three years have trended slightly above that, but nowhere near this year’s number. Keep in mind that Greinke isn’t exactly a high strikeout pitcher either (7.81 K/9 this year; 8.09 K/9 in his career), so it’s not like he’s doing this all by himself. Circle back to a slightly above average defense as noted earlier and it isn’t the eight other Dodgers on the field either. Left on base percentage is important to use in conjunction with HR/FB rate (7.1%) and BABIP (.247), both of which are below career and league averages.

While I’m not predicting impending doom for Greinke, there is disconnect between his ERA of 1.58 and his xFIP of 3.25. This is supported by the above evidence, so I can say with some confidence that owners should expect some regression as the second half of the 2015 season approaches.

Adam Sutton is a correspondent at FantasyPros. To read more from Adam, follow him @DraftStars_Adam. You can find more of Adam’s work at DraftStars.net.