Ryne Nelson’s recent success has stabilized the Diamondbacks starting rotation

Ryne Nelson has been the rotation’s unsung hero over the past six weeks. Since May 29, Nelson is 3-3 with a 4.30 ERA/4.16 FIP. In nine appearances, eight of them starts, he’s pitched 52 1/3 innings and has gone at least six innings. Only 10 pitchers have accumulated 50 innings over that stretch, which includes All-Star Game starter Paul Skenes and fellow All-Stars Logan Gilbert, Logan Webb, and Tarik Skubal. Of those 10 pitchers, Nelson ranks eighth in ERA.

Injuries have been the main story with the Diamondbacks’ starting rotation in the 2024 season. The team has missed Eduardo Rodríguez, Merrill Kelly, Zac Gallen, and Jordan Montgomery at varying points in the season. Brandon Pfaadt, the one constant in the rotation all season, has stepped up to provide quality innings every time out.

Sometimes the raw ERA may not tell the performance, as where a pitcher pitches can be just as important. If we use FanGraphs’ park-adjusted ERA metric (ERA-), Nelson has a 105 ERA-. That means he’s about 5% worse than the average pitcher at preventing earned runs. Considering the volume of innings, the current state of the rotation, and where Nelson is in his career, those are all very positive developments.

The 26-year-old right-hander is still far from a finished product. He’s been trying to develop his secondary pitches at the major league level after his “plus-plus” quality four-seamer got him there. It’s been a bumpy road in that department, but his ability to command the fastball better has been a huge reason behind this recent success. He credits that to a recent mechanical adjustment on the mound.

“Just trying to calm down the body and allow the arm to work out in front,” said Nelson in the postgame coverage on Dbacks TV following Friday’s 5-4 win over the Toronto Blue Jays. “I think that’s helped with not only command, but velocity too, and just letting the arm play.”

The next step in the right-hander’s development as a starting pitcher will be his ability to command his slider, curveball, and changeup. The cutter is more of a “get off the barrel” type pitch meant to induce weak contact with not many whiffs. He’ll need to generate more swing-and-miss from those three secondary pitches, as the changeup is the only pitch with a whiff rate above 20%. Otherwise, his ceiling is a swingman or a middle-inning bridge reliever between the starter and the back of the bullpen.

Nelson will have plenty of opportunities to hone his craft, with at least five to six more starts before someone else threatens to take his rotation spot. That time won’t come until the middle of August, when Rodríguez and Kelly are potentially due back from their respective shoulder injuries.