Aidan Miller's sore back limits Grapefruit League availability for Phillies

Aidan Miller, the 21-year-old Phillies No. 1 prospect and MLB Pipeline No. 23 overall, has been limited in Grapefruit League action after waking up with a "super tight" lower back the week of Feb. 24, and the club scratched him from a planned Dunedin lineup on Saturday while he receives treatment. The back issue kept Miller out of the Phillies' two Grapefruit League games over the weekend and tempered a spring plan that included work at both shortstop and third base.

Miller told The Philadelphia Inquirer that he "woke up with a 'super tight' back one day last week and the feeling did not go away after treatment," and he added he "felt it last season" as well. Manager Rob Thomson described the club's approach plainly after the Phillies' spring exhibition versus the Pirates: "We’re just being super cautious with him, obviously, this early in camp," and "He’s just getting treatment." Thomson also addressed a hit-by-pitch during live batting practice, saying, "It wasn’t in the back" and "So I don’t know if he jarred it or something trying to get out of the way."

RotoWire and other outlets reported Miller has been ramping up activity in the weight room but emphasized the medical limits to on-field work. RotoWire summarized reporting from the Inquirer and team sources with the line, "There’s no timetable for when Miller (back) will resume swinging a bat," and noted that, with no timeline for hitting, it "could be a while before we see the top prospect in Grapefruit League action."

The Phillies and analysts have quickly translated limited camp availability into roster implications. Multiple outlets, including MLB.com, RotoWire, Sports Illustrated, and PhillyVoice, indicated Miller is very likely to open the 2026 season with Triple-A Lehigh Valley. RotoWire called that outcome "close to a foregone conclusion," PhillyVoice wrote the already slim chance he made the Opening Day roster "seems just about zero now," and the Inquirer noted Miller entered camp as a long shot to crack the big-league roster even before the back soreness.

Miller’s 2025 minor-league resume frames the organizational patience: at Double-A Reading he reached base at a .382 clip and stole 52 bases, and in an eight-game Triple-A stint he went 9-for-27 (.333) with a .514 on-base percentage. The Phillies drafted him in the first round in 2023 and have used him exclusively at shortstop in the minors; spring plans called for added reps at third base as the club projects a potential path to third base in 2027 if development continues and Alec Bohm departs after the 2026 season.

Bryce Harper injected a teammate-level push in a midgame spring interview, saying in part, "I need him to get healthy because he can help us by the end, obviously." For now the organization is weighing that upside against immediate caution: Miller is receiving treatment, increasing weight-room work, and remains without a timetable to resume hitting, making Triple-A the likeliest staging ground for his 2026 season while the Phillies monitor recovery and roster needs.