Diamondbacks Give Ryne Nelson and A.J. Puk Timelines

Once again June has not been a kind month for the Diamondbacks on the pitcher injury front.

May 19, 2026; Phoenix, Arizona, USA; Arizona Diamondbacks pitcher Ryne Nelson (19) reacts after giving up a solo home run against the San Francisco Giants during the second inning at Chase Field. Mandatory Credit: Joe Camporeale-Imagn Images | Joe Camporeale-Imagn Images

Arizona Diamondbacks manager Torey Lovullo clarified the injury diagnosis and timelines for Ryne Nelson and A.J. Puk on Friday afternoon. While Nelson's injury is not the worst case scenario, as Nelson said earlier, it's still going to take a while.

Ryne Nelson's Injury Diagnosis and Timeline

Jun 15, 2026; Phoenix, Arizona, USA; Arizona Diamondbacks pitcher Ryne Nelson in the first inning against the Los Angeles Angels at Chase Field. Mandatory Credit: Mark J. Rebilas-Imagn Images | Mark J. Rebilas-Imagn Images

Nelson has a flexor tendon strain and also a mildly sprained UCL. Lovullo declined to put a number on the level of the strain. But he did offer a timeline.

He said that Nelson would be shut down from throwing for at least 4-6 weeks, and that at the six-week point he would receive another MRI.

Lovullo explained the process to get a pitcher back up and in a game once they've had that much time off.

"It's usually one to one, right? If it's a four-week shutdown on the backside, it's a four-week buildup on the other side."

Since Nelson will not be getting his follow up MRI until the six-week point, that would lead one to believe he'll need six weeks to ramp back up. Asked if that means it could be mid September until Nelson returns, Lovullo answered in the affirmative.

"Yes, when I'm doing my own manager math, yes, that's where I'm at. Unless there's something that comes up out of nowhere," Lovullo said.

A.J. Puk Diagnosis and Timeline Update

Arizona Diamondbacks left-hander A.J. Puk (33) reacts after closing out their 10-6 win against the Chicago Cubs at Chase Field in Phoenix on Sunday, March 30, 2025. | Joe Rondone/The Republic / USA TODAY NETWORK via Imagn Images

As previously reported, A.J. Puk had been shut down and was awaiting second opinions on his shoulder injury. That diagnosis has come back as a shoulder capsule sprain.

He is shut down from throwing for four weeks, after which he'll receive a follow-up MRI. From that point, using Lovullo's math, it will be another four weeks for Puk to get back up to speed. So the earliest we might see him, barring any setbacks, would be some time in mid-August.

Sunday Starter Not Likely to Be Brandon Pfaadt

Apr 5, 2026; Phoenix, Arizona, USA; Arizona Diamondbacks pitcher Brandon Pfaadt (32) pitches during the first inning at Chase Field against the Atlanta Braves. Mandatory Credit: Arianna Grainey-Imagn Images | Arianna Grainey-Imagn Images

While Brandon Pfaadt is scheduled to start for the Triple-A Reno Aces on Saturday, it did not sound like he will be the one to get the ball on on Sunday in place of Nelson.

Pfaadt threw 3.1 innings and 45 pitches in his last outing. That does not leave him stretched out enough to make the start at Chase Field on Sunday.

"We want to make sure that when and if he gets back here, that he's built out to a certain number of pitches. [45] pitches is not a great spot, a great number for him or us." Lovullo said.

The D-backs do have the option of simply moving Merrill Kelly up from Monday to Sunday, as that would still be four days rest thanks to the off day on Thursday. But they've not yet made that decision.

"If we decide to go another route from pushing everybody up on Sunday, and we do insert a starter, that person is going to have a full load of pitches."

That seems to preclude Pfaadt then. Stay tuned to Arizona Diamondbacks ON SI for further updates.