Ryan Thompson’s Woes Deepen Pressure on D-backs’ Relief Corps

When looking at the Arizona Diamondbacks' bullpen, one of the pitchers who has underperformed expectations this season is right-hander Ryan Thompson. In his first 19 appearances, Thompson has a 7.50 ERA and -0.6 bWAR.

Once a key piece in the 2023 bullpen that went on a strong run and fueled Arizona's run to the World Series, he's become the face of the unit's 2025 struggles. Advanced metrics aren't necessarily more bullish, as he has a 5.30 FIP and 4.88 xERA on the season. FIP takes into account the four true outcomes: strikeouts, hit-by-pitches, non-intentional walks, and home runs, while xERA incorporates quality of contact metrics to go with strikeout and walk rates.

The struggles for Thompson have been more recent. In his first 14 appearances, he had a 3.68 ERA and 3.49 FIP, and the team had a 10-4 record. In his five outings since, Thompson has recorded only 10 outs and surrendered nine runs on 11 hits. He's given up runs in four of those five appearances, with multiple runs in three. The Diamondbacks have gone 2-3, with him playing a key role in all three losses.

Thompson's struggles have negatively impacted the bullpen. In his last appearance, which was supposed to be a "get right" game against the bottom of the Dodgers' lineup, he only got two outs before a 9-3 game turned into a save situation, forcing manager Torey Lovullo to send in his closer to get the final out. The cascade effect from that appearance may have affected Miller's performance in the following game, his third in as many days, as he blew a two-run lead and was walked off.

When examining the struggles of a pitcher who's previously performed well, it's important to look at all aspects of his game. The positives for Thompson are that he's getting chases outside the strike zone. His 34.3% chase rate and 27.7% whiff rate rank in the 93rd and 68th percentiles amongst major league pitchers. The combination of solid chase and whiff rates has translated to a 20.7% strikeout rate, which would be his highest rate since joining the Diamondbacks in 2023.

Thompson's problem, however, is when batters make contact. The biggest issue is a steep drop in ground ball rate. Per Statcast, Thompson's ground ball rate in the previous two seasons was 62.5% and 62.7%. In 2025, that number has dropped to 45.7%, a severe decline of 17% compared to last season.

As a direct consequence of a decline in his ground ball rate, opposing hitters have a .316/.379/.532 slash line with four home runs over 18 innings. Last season, he allowed just five home runs in 66.1 innings.

All four home runs have come on location mistakes with his secondary pitches, three on sliders and another on a splitter. Two of the three sliders were middle-middle pitches to right-handed hitters (Eli White and Jordan Beck). The other two home runs came on down and in pitches to a left-handed batter. Shohei Ohtani bats .600 with a 1.800 slug, and Francisco Lindor hits .375 and slugs .938 in that particular zone.

While it can be easy to chalk up the struggles to location mistakes at inopportune times, there's a concerning trend with Thompson's bottom-line results with his sinker. In 2025, the pitch has been hit hard when it's been in the strike zone, especially in the bottom third of the zone.

Usually, that's a good spot for a sinkerballer to live, as that typically leads to a lot of ground ball contact and outs. That has not been the case for Thompson, as teams have become more successful at getting the barrel of the bat to that part of the strike zone and making better contact. Opposing hitters are batting .579 with a .737 slugging percentage on sinkers in the lower third of the zone.

The main reason has been the average exit velocity against those pitches is trending in the wrong direction, going from 89.0 in 2023 to 92.4 in 2024 and 98.5 MPH in 2025. While the launch angle on those pitches has remained consistent year-to-year, the increased exit velocity has led to more hits. While he's yet to surrender a home run on the sinker, it has been responsible for 17 of the other 21 hits he's allowed this season.

This speaks to the limited shelf life of pitchers who rely on deception and unique arm angles to get hitters out. With the introduction of Trajekt Machines, the adjustment period for hitters has become much shorter. That will force pitchers like Thompson to constantly adapt to remain one step ahead of hitters to remain effective.

We've already seen more drastic changes to Thompson's arsenal this season. He's throwing his sinker a lot less, with the usage down from 64.2% last season to 48.0%. His slider usage has spiked to 44.2% as a result. It's been an effective pitch when he locates it, as batters are hitting .176 with a 29.3% whiff rate. But at the same time, he's been burned by location mistakes on his slider.

He's also started dabbling with a splitter, though the two he's thrown were a ball well out of the zone and a go-ahead three-run home run against Ohtani. That speaks to an ongoing failure to develop a reliable third pitch in his career. He experimented with a changeup in his time with the Tampa Bay Rays but found little success using it and shelved it in his tenure with the Diamondbacks.

With how tight the National League Wild Card race is, and every game matters, the team can ill-afford to have Thompson remain a huge liability in their bullpen and still contend. If Arizona waits too long for a turnaround that never happens, it could either cost them a playoff berth for the second straight season or force them to part with significant prospect capital to replace him.