Kyle Muller, Comps, and Projections

New A's left-hander Kyle Muller was compared to former Giants lefty Madison Bumgarner after his first bullpen in camp, but how does that comp hold up by the numbers?

A's manager Mark Kotsay told reporters over the weekend that newly acquired lefty Kyle Muller shares some similarities to Madison Bumgarner on the mound. 

He told Martín Gallegos, “They share a lot of the same qualities and traits. I know Bum rides horses. I don’t think Muller’s on horses yet. But they both like to hunt. They’re both left-handed and they’re both really big. If Muller can find a way to turn out like Bum, we’ve got something there. We’re excited about watching him throw.”

With Muller coming over as part of the Sean Murphy trade, this could be Kotsay's way of pumping his new guy up a little bit, but I wanted to take a look at see what similarities could be found statistically between Muller and a 25-year-old MadBum, as the A's lefty heads into his age 25 season.

Muller is 6-foot-7, 250 pounds, while MadBum is currently listed at 6-foot-4, 257. 

In terms of pitch mix, Muller offers a 94 mph fastball, a slider that sits 87, a curve that drops in at 81, and a changeup at 88. At 25, Bumgarner was primarily a fastball, cutter, curve pitcher, but he also threw a handful of changeups and sliders over the course of the season. 

The most notable difference off the bat is that Muller throws just a little harder. One mile per hour difference on the average fastball, two mph on the change, and four mph on the curveball. The other difference being that Bumgarner has always utilized a cutter as well.  

The biggest difference between them has to be their command. Bumgarner was finishing near the top of the league in BB% in 2015, walking just 4.5% of the batters he faced. Muller, in his very limited time in the big leagues, has walked 12.9% of the batters he faced in 2021, and 13.6% of them in 2022. For what it's worth, those totals came over 49 total innings across two seasons. 

Needless to say, a lot would have to change for him to reach Bumgarner's walk rate. 

In doing some research for this piece, there was another pitcher that was compared to Muller that had a history of walk issues over at Baseball Savant, and that is the 2021 version of Robbie Ray. More specifically, the year that he won the AL Cy Young. Savant came to this conclusion based on velocity and movement, and they were specifically pulling from the 2021 version of Muller to draw that comparison. 

Before that year, Ray had always had trouble with command. In 51.2 innings in 2020 he had a walk rate of 17.9%. The following year it was down to 6.7% with the Blue Jays. 

Ray worked on his mechanics and bulked up a little for that special season, but he was also working with a tremendously effective tunnel on his pitches. 

Tieran Alexander of Prospects Live wrote an article last August detailing some of the work they'd done on tunneling, and what makes an effective tunnel. 

For a slider/four-seam combo, they say that a pitcher needs to have two of three elements to effectively tunnel their pitches: 6-14" of horizontal separation; 8-16" IVB separation; 6-11 mph separation. In 2021 Robbie Ray had all three of these factors working for him, which led him to a 2.84 ERA with a 1.04 WHIP in 193.1 innings.

To this point, Kyle Muller hasn't gotten there with his tunneling, at least according to the research that Prospects Live has done, and the results we've seen from the A's lefty seem to support that. Opponents have hit .275 and .290 against his fastball in the big leagues, granted in a small sample, but getting his slider and fastball in sync could do wonders for him moving forward.

In his 12.1 innings with Atlanta last season, Muller's velo separation was 7.3 miles per hour, which is within the 6-11 mph that is suggested, but that's the only mark that he clears. His horizontal movement is only separated by 4.6 inches, so he'd need another inch and a half to reach his goal horizontally. Vertically, he has a separation of 17.6 inches, or 1.6 above what's recommended. 

The good news here is that he's not that far off from achieving all three factors. It would take some work and some pitch shaping to find the right mix, but it would be doable. 

Over at FanGraphs, ZIPS has Muller projected to get into 25 games (24 starts) and finish with a 3.93 ERA over 123.2 innings. They also have his walk rate much more in line with what it has been at the minor league level, at 3.78 walks per nine. That rate is still a touch high, but well below the 7.84 per nine that Robbie Ray finished with the year before his Cy Young season. 

If you enjoy conversations about pitch tunneling, I recently recorded an episode of Locked on A's, talking about Ken Waldichuk's quest to add velocity this season and why it could lead to more success in 2023!