Aidan Miller has a diagnosis and a new target in his rehab process.

The Phillies announced Wednesday that Miller, the organization’s top-ranked prospect, has been diagnosed with discogenic pain and facet inflammation in his lumbar spine. He will undergo a minimally invasive procedure Friday called a radiofrequency ablation of the facet joints.

Miller will rest for one week after the procedure, then return to his rehab with the goal of getting back to game activity in six to eight weeks, according to the team.

Miller has not played in a game this year. The back issue kept him out of Grapefruit League action and delayed what was expected to be his first full season at Triple-A Lehigh Valley.

The Phillies said Miller had a recurrence of low back pain when returning to baseball activities and was seen by spine specialists over the last couple of weeks. The specialists agreed that the procedure was the recommended course of treatment.

Phillies general manager Preston Mattingly said Sunday at Dodger Stadium that Miller was still in his rehab program, was not doing baseball activities and had not swung a bat.

“I think we’re leaning on medical,” Mattingly said Sunday. “Still just doing his rehab program at this point. Not baseball activities.”

Miller had been playing catch and doing some ground-ball work during the year, but had not resumed hitting.

The procedure is a significant development for a player who entered the year with a chance to push toward Philadelphia if everything clicked.

Miller, who turns 22 on June 9, is coming off a strong 2025 season between Double-A Reading and Triple-A Lehigh Valley. He slashed .264/.392/.433 with 43 extra-base hits and 59 stolen bases in 116 games.

His finish created much of the anticipation entering this season. Over his final two months, Miller posted an OPS over 1.100 and had 22 extra-base hits in his last 36 games.

Now, the Phillies have a clearer plan after a slow-moving rehab process.

If Miller returns to game activity in six to eight weeks, his first game of the season would come sometime in late July or early August.