The Atlanta Braves made some waves this off-season with acquiring Sean Murphy, and Joe Jiménez. Sean Murphy has been excellent, and Jiménez is arguably not performing his best. But, it can easily be said that neither of these performances have been the most surprising performance from a player acquired this off-season.
When the Braves signed Michael Tonkin to a minor league deal, most fans probably just chalked it off as a pure depth move. After all, he has not played in the majors since 2017, and his last action was in 2021 where he played in the Mexican League. On top of that, he had a career 4.43 ERA and 4.57 WHIP in 146.1 innings in his time in MLB before signing with the Braves.
The Braves took a shot on Tonkin this off-season and it is paying dividends. He currently is sporting career bests in walks per nine innings, hits per nine innings, WHIP, and strikeout to walk ratio. His ERA and FIP are the second best of his career other than his 11.1 inning cameo in his 2013 rookie season.
Currently at the time of this writing, Tonkin has a 1.89 ERA, 3.61 FIP, 0.579 WHIP, 1.4 walks per nine innings (4.5 percent), and 7.1 strikeouts per nine innings (22.7 percent). Not bad for a pitcher on league minimum salary.
Relief pitching stats are volatile
Since relief pitchers have much smaller sample sizes than their rotation counterparts, it can result in some massive gaps between XSTATS and on field numbers, especially this early in the season, so it is always a good idea to see what the underlying metrics display.
This performance by Tonkin has been unexpectedly excellent, but will he be able to keep it up? Digging into his Statcast profile, we can find some indicators.
Right off the bat we can see that his xERA is promising at 2.68. This is not as low as his actual ERA (1.89), but it is still very good. Is in the top 12.0 percent in the league. Just like his ERA, there is a gap between his wOBA against and xwOBA against, which is another high level way of looking at if a player is due for regression or progression.
Currently his wOBA against of .183 is top 2.0 percent of the league. His xwOBA against him is higher at .257, but still is top 12.0 percent of MLB.
Looking at these two metrics we can see that he is due for regression, but if continues to pitch at the same rate, it should not be big regression. It makes sense why Snitker keeps giving him innings.
Let’s explore his profile and see how Tonkin is able to keep his ERA and wOBA so low
First, we already know his walk rate is good, but when compared to the rest of the league it really shows how good. His walk rate is among the best 12.0 percent (there is that magic 12.0 again) of MLB pitchers. Limiting base runners obviously helps your ability to keep runs off the board.
Walks seem pretty obvious, but then we look at how hard hitters are hitting the ball against Tonkin. This one is a bit of a head scratcher at first. Hitters’ average exit velocity against him is high. In fact Tonkin is in the bottom 24.0 percent in Average EV against and bottom 33.0 percent in Max EV. Tonkin is also bottom 28.0 percent in Whiff percentage, showing that he is not missing many bats. Yet, his xSLG against ranks among the best 29.0 percent and his xBA against ranks in the best 22.0 percent. So, what gives?
Typically, when a player is hitting the ball hard against a pitcher and also have low swing and miss rate, the pitcher’s xSLG and xBA are not good. This is not case with Tonkin.
What is interesting is that although the swing and miss rate is low, he has an excellent chase rate. In fact, his chase rate is ranked in the top 24.0 percent of MLB pitchers.
This has seemed to produce a very unique profile. Batted ball types are not an as well talked about aspect of hitting as other areas. But, they are important, and Tonkin’s results are a perfect example.
Jonathan Metzelaarwrote an excellent article titled “Beyond the Barrel: An Introduction to Ideal Contact Rate” that does an exceptional job explaining ideal contact. (Please read this article, it is well worth your time).
Tonkin’s success has been due to ability to create poor contact. Typically when you hear “contact pitcher” you may think of a groundball pitcher. However, Tonkin is taking a completely different approach that has been successful thus far.
In the below graphic from Metzelaar’s article, is an excellent chart which shows launch angles and how the correlate with contact types (topped, under, flares/burners, etc.).
With his sinker/slider combo, Tonkin has been able to keep the flare/burner percentage down to 18.8 percent. That’s just over five percent better than league average. Flare/burners are the second best type of batted ball that produce approximately a .659 batting average. These are sharply hit grounders and line drives that fall for hits. You can see in the launch angle graphic as to why these types of batted balls have great results for hitters.
Tonkin also has been able to get hitters to hit bad fly balls at a very high rate. He has an Under percentage of 35.4 percent, which is almost eleven percent better than league average. A batted ball designated as “Under” has the lowest expected batting average of any batted ball type.
The intriguing part in all of this is that typically a sinker heavy pitcher is trying to get grounders, but Tonkins has found a way for hitters to get under his pitches at a high rate. His sinker has an insane added run value of -7 in only 150 pitches. Hitters have a .030 batting average (xBA of .153) and .081 wOBA (.227) xwOBA against it. He pitches this pitch 60.6 percent of the time.
Hitters are hitting this pitch hard at 45.8 percent of the time (which is why his average EV is so bad), but the average launch angle is thirty degrees. Hitters are hitting routine fly balls at an extremely high rate. In fact, his fly ball rate (including his slider) is 29.2 percent, which is approximately six percent higher than league average over the past five years.
As stated earlier, relief pitcher performance is extremely volatile. However, Tonkin’s underlying metrics show that his performance thus far has not been a fluke.
He is having success in a very unique way by limiting hitters by forcing them to hit into routine fly balls at a high rate, using his sinker (of all pitches). This combined with a very low walk rate has resulted in limiting runs, and base runners at a rate that any manager would be happy to have.