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Checking in on Joe Jiménez

Jiménez has been a solid force this season. Let’s look at his underlying numbers.

MLB: Miami Marlins at Atlanta Braves
Joe Jiménez is dealing
Dale Zanine-USA TODAY Sports

The Trade Deadline has come and gone and now the Atlanta Braves are in the final stretch of the season. The Braves did not add any flashy players, but when a team has the roster that the Braves do, there are not many holes to fill.

Likely one of the reasons the Braves front office did not feel pressure to add more at the deadline has been the strength of their bullpen which currently has the best ERA in the National League. Of course, ERA is not an end all, be all stat, but it is safe to say the bullpen is not a weakness.

A key member of this solid bullpen may be surprising to some. Joe Jiménez has established himself as a steady presence for the Braves this season with a 2.61 ERA, 3.21 FIP, 29.6 percent strikeout rate and a 0.5 fWAR in 38.0 innings pitched.

Just looking at ERA, he has been almost a full run better than last season in which he had a 3.49 in 56.2 innings pitched.

Let’s explore if this success should be expected to continue, and see what has changed since last season (other than uniforms of course).

There was a reason the Braves wanted Jiménez

Looking at Jiménez’s surface numbers last year, he by no means had a bad season. He has a 3.49 ERA after all, but his underlying metrics showed that he was actually unlucky in terms of preventing runs. In fact, his xERA was much lower at 2.90. Also, his battening average against in 2022 on all of his pitches was .226 while his xBA was lower at .216.

This was due to multiple variables. A few that really stick out was that he had a very low strand rate at 67.4 percent. According to Fangraphs, left on base (LOB) percentage typically sits around 72.0 percent.

One other area that pointed to Jiménez having better luck in the ERA and batting average against department was that his BABIP against in 2022 was .328, while his career average was .311 and league average in 2022 was .298.

He also had one of the best strikeout rates in MLB being in the top 5.0 percent, with his walk rate of 5.6 being the lowest of his career.

This faith in Jiménez being able to regress towards to mean (progress, if you will) based purely on the fact that he was unfortunate has paid off in spades in terms of run prevention.

In his last twenty-one appearances, Jiménez has only given up two earned runs. He also has only given up more than one run in an appearance once all season.

Jiménez has the lowest ERA of his career of 2.61 in 38.0 innings pitched. In terms of adjusted ERA, that is 78.0 percent He sports an excellent 1.105 WHIP, which is second best of his career (1.094 in 2022), and the second best SO/W ratio of his career with 4.27 (5.92 in 2022).

We should not be shocked if we see some drop off in run prevention

Just like in 2022, Jiménez’s surface numbers are quite different than his XSTATs. But, this time, in the opposite manner. This season he has an xERA of 3.75 and an xBA of .223 versus an actual batting average against of .215. His xSLG is also higher this year at .400 versus .345 in 2022.

These drop offs in XSTATs are due to a few factors. First, Jiménez had an insanely low solid contact rate of 2.8 percent in 2022, which has come back to earth to 9.0 percent this season. The MLB average is 5.8 percent.

Next, the opposite of what happened with his LOB and BABIP in 2022 are happening in 2023. He currently has a much higher LOB rate of 77.5 percent and a BABIP of .281, showing that he has been a bit lucky in both stranding runners and ball that are in play.

His pitch percentage on his three pitches are almost identical to last year, so his arsenal changing is not the reason why we are seeing a drop off in his underlying metrics.

But, hitters are hitting all three of his pitches harder this year than last year.

Hard Hit Rate by year

Hitters are also chasing all three of his pitches less this season than last.

Chase Rate by year

What is interesting is that both his fastball and slider both have been thrown in the strike zone at almost the exact same rate this season as last (within 0.6 percent on both pitches). The only pitch that he is missing the zone with more is his changeup, and he only pitches that 6.0 percent of the time.

The only major change is that his fastball has lost some horizontal movement. In 2022 he had 10.4 inches of break, which was 2.7 inches more than average, but this season it has dropped from 10.4 to 8.9 and is 1.8 more than average. However, hitters are not hitting it much better.

As can be seen in chart below, his xwOBA of .311 against his fastball is right on par with last season. It is his slider that hitters are having more success with.

xwOBA by season

This has stemmed from barrel percentage. As a refresher, a “barrel” is when a hitter makes contact with a ball and it has an xBA of .500 or better. In 2022, hitters had a barrel percentage of exactly 0.0 percent on his slider. This season, it has spiked to 12.5 percent of the time. This is the highest of his career.

Bingo! Hitters are seeing his slider better this year and are hitting it with much better quality than they have in the past. Jiménez currently pitches his slider 31.2 percent of the time.

In Summary

Jiménez has been excellent this year. The Braves made the right move in trading for him. His bad fortune from 2022 has turned into good fortune in 2023.

Hitters have adjusted to his slider and are hitting it well. If he does not adjust soon, odds point to us seeing a drop off in his ERA and other surface numbers eventually. However, even if they drop off some, he is still pitching at an elite level, and hopefully will continue to do so.

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