Zack Greinke is not what he used to be

Last season with the Los Angeles Dodgers was the best season of Zack Greinke's career. His 1.66 ERA was the lowest in a season. And he pitched 222⅔ innings, topped only by 229⅓ in 2009.

But on Thursday night against the Colorado Rockies, he put up a modest line, allowing three earned runs in 5⅔ innings. It was part of a concerning trend.

So why then is Greinke not what he used to be?

His fastball has lost its bark

The most notable change in Greinke’s approach with the Arizona Diamondbacks is that he is throwing his slider more than last year while throwing fewer fastballs.

Throwing more sliders isn’t hurting Greinke, though. The problem has been that his fastball has been easier to make contact with, and it’s leading to a lot of damage against him, as noted in the chart below.

Only six qualified starters have allowed hard contact more frequently than Greinke this season on fastballs.

Having problems staying away

One of Greinke’s greatest strengths last season was throwing pitches on the outer half of the plate.

Last season, 75.3 percent of Greinke’s pitches were thrown on the outer half of the plate or further away. This season, that number is down to 65.7 percent.

Greinke has still had success on those pitches, limiting opponents to a .668 OPS in plate appearances to end in a pitch in that location. However, that is 182 points higher than he allowed last season.

This has also hurt Greinke on pitches on the inner half of the plate. Opponents have made hard contact 16.3 percent of the time against pitches thrown by Greinke on the inner half of the plate, up from 10.6 percent last season.

The process is getting better

Greinke is starting to solve a lot of the problems he had early in the season.

However, Greinke’s solution hasn’t been to revert back to what he was doing last season. In fact, he has actually separated himself more from those trends.

In his past five starts, Greinke has thrown his slider 28.9 percent of the time, up from 20.2 percent in his first 11 starts.

Greinke is improving as the season pushes forward, but he isn’t the pitcher he was last season. He has a new approach that is beginning to work in his favor.