Sunday Snakes: Bummed Out About the D-backs Rotation

The Diamondbacks may face a tough decision for their starting rotation soon.

The Diamondbacks will be facing an interesting decision with their rotation coming up, due to Madison Bumgarner struggling in his first three starts in 2023. In 13.2 innings, Bumgarner has allowed 13 runs (12 earned) on 18 hits with eight strikeouts, and 11 walks. Advanced ERA metrics back up his 7.90 ERA, with a 7.71 FIP, 7.25 xFIP, and a 8.69 xERA. This continues a troubling trend for the veteran left-hander, who pitched to a 6.50 ERA and 5.25 FIP in the second half of 2022. 

Delving deeper, we take a look at Bumgarner's 10-game rolling average for ERA and FIP since the start of the 2022 season to see where things have gone south.

Initially Bumgarner overperformed his FIP in his first 10 starts, but the ERA regressed towards his peripherals. Then he had a tough month of August, in which he allowed 28 runs (27 earned) in 26.1 innings. That kickstarted a negative trend in his rolling average for both ERA and FIP, with both metrics climbing out of control without much hope in improvement. Since August 2022, Bumgarner has made 12 starts with an ERA of 7.40 and an FIP of 5.90.

It has been a hard fall for the 33-year-old lefty, who carved out an impressive legacy early in his career with the San Francisco Giants. 

After his last start against the Miami Marlins, we were all left wondering how much rope left does Bumgarner have if he continues to struggle?  The team has already announced he'll make his next start as scheduled Wednesday against the St. Louis Cardinals. Given Lovullo's comments about pitch counts with Merrill Kelly and Drey Jameson this week, it appears the organization is hesitant to commit to a move and tap further into their starting pitching depth after losing Davies to an oblique strain that Lovullo told The Arizona Republic's Nick Piecoro was more than a Grade 1. 

D-backs general manager Mike Hazen said in February that a "successful" season would mean the team would be buyers at the trade deadline and competing for a playoff spot well into September. At some point, they will come to a head with Bumgarner's poor performances and have to consider if a move needs to be made to stay on pace for that goal. Should Arizona decide to pull the plug, they have two candidates in Triple-A that could be called up to the rotation in left-hander Tommy Henry and right-hander Brandon Pfaadt. 

Henry is 0-0 with a 7.63 ERA and a 16/8 strikeout to walk ratio in 15.1 innings. He has gone at least five innings but not allowed fewer than four runs in all three of his starts with Reno. He made nine starts in the big leagues last season, pitching to a 5.36 ERA and struggled to locate his mostly average stuff to the edges of the strike zone. 

Pfaadt is 1-1 with a 5.40 ERA and a 17/3 strikeout to walk ratio, but has served up five home runs on the season. He hasn't quite been able to get the feel for his impressive array of secondary pitches, but is trending up after allowing just three runs in his last 9.2 innings. Pfaadt would require a 40-man roster move to call up to the big leagues, but in this situation the active and 40-man roster move would be the same. 

Slumping Hitters

The Diamondbacks have gotten solid contributions from the lineup with Josh Rojas, Nick Ahmed, Geraldo Perdomo, and Evan Longoria this season. Outside of those four, the team hasn't gotten consistent production from their lineup. The three players that they really need to get going are first baseman Christian Walker, outfielder Jake McCarthy, and outfielder Lourdes Gurriel Jr. 

Walker got off to a slow start in the bottom line numbers last season, but had better batted ball data underlying a lot of poor batted ball luck. This season he doesn't have the same quality of contact, but has still plenty of at-bats to turn that around. The biggest difference is Walker is mostly either rolling over to the left side of the infield and hitting pop-ups. Neither form of contact is very good for a hitter like Walker. 

Walker is also likely expanding his own zone, as his chase rate has worsened from 23.1% to 27.5%. That could be a case of chasing barrels, ultimately mishitting mistake pitches into foul balls and easy outs. However it appears he could be coming out of that slump, as Walker had a pair of line drive hits against reigning Cy Young winner Sandy Alcántara on Sunday, including an RBI double that helped break the game open. 

McCarthy's timing hasn't looked quite right this season, although his plate discipline numbers hold up pretty well compared to the rest of the league. He's swinging at strikes, but the issue is not about balls and strikes but perhaps not being selective enough at the plate. Of the 155 pitches McCarthy has seen on the season, 79 (51.0%) are in the shadow zone. Those pitches are strikes, but typically not pitches a batter can do much damage with. Of those 79 pitches, McCarthy has swung at 43 of them and has a .161 wOBA. There are obvious situations where he may need to swing at a pitch in this region, when making contact is more valuable than taking the pitch, but in a situation where he's looking to do damage or ahead in the count he'll need to be more selective.

Gurriel is the one hitter who does have some encouraging xStats of the group, with a lot of pink in his profile. His hard-hit rate of 42.9% ranks in the 60th percentile while his xwOBA is in the 55th percentile. There may be some hope for future regression in his overall numbers, but his platoon splits based on the handedness of the starting pitcher are very concerning. Gurriel was brought in to bring some more protection against left-handed starters, but has hit .148/.179/.185 in games started by a lefty. He's had reverse platoon splits the past two seasons, and that trend is continuing to begin the 2023 season. 

Corbin Carroll's Wild Start

So far, Carroll's rookie season has been a wild roller coaster ride. He's flashed the talent of an All-Star player, but there are clear areas of improvement for him in order to reach that point. 

He hasn't had too many issues making loud contact this season, as evidenced by his team-leading four home runs and .404 xwOBA on contact. The major concern will be what happens when he's not squaring up the ball. So far Carroll has yet to draw a walk through 16 games, which has limited the number of opportunities for him to make an impact as a baserunner. 

It may be a case where the spot in the order is dictating his approach at the plate, with him being more aggressive batting in the middle of the D-backs order instead of the top. That could change in the near future, as Carroll's skill set is better suited for the top of the order. 

One area that hasn't been much of a concern is hitting lefties, as Carroll is 8-for-21 (.381) with a home run. His home run came off future Hall of Famer Clayton Kershaw on April 7th. He had big platoon splits against lefties last season, both in the minors and majors, so this is a great step in the right direction.

If Carroll can improve his on-base ability without sacrificing the impactful contact he's been making, he'll find himself as a mainstay at the top of the order regardless of who's pitching.

Prospect Graduations

With Corbin Carroll, Ryne Nelson, and Drey Jameson all regulars in the starting lineup or rotation, it's time to promote them from prospect status. All three players have looked solid out of the gate and figure to be a big part of the team for at least the next three to four years. With their graduations, replacing them on my Top 30 list are right-hander Dylan Ray, right-hander Yilber Diaz, and outfielder Caleb Roberts. 

Ray is a former fourth round pick who missed his freshman season at Alabama due to Tommy John surgery, was drafted due to the promise and stuff he showed his sophomore season. he has a mid 90s fastball that comes with a downhill angle and late arm-side run. His main secondary pitch is a slider, but also throws a changeup. He's made two solid starts with High-A Hillsboro and may have the most helium potential of all the pitching prospects with a good season.

Yilber Diaz has the stuff that could play in the backend of the bullpen. His fastball touches triple digits with a slider as his main secondary offering. He has one start, allowing one run in 3.1 innings with four strikeouts and three walks.

Caleb Roberts is a converted catcher who has increasingly seen more time in the outfield. He's currently playing for Double-A Amarillo and is hitting .294 with two doubles, two triples, and a home run in eight games.