Instead of getting ready to add Ian Hamilton to the major league roster, the Yankees are facing some uncertainty in the bullpen after the right-hander was scratched Friday night from what was expected to be his last rehab outing.

Hamilton reportedly experienced back spasms and did not appear in Friday night's game at Double-A Somerset. The 29-year-old reliever has been working his way back from a right lat strain since June.

Hamilton was recently placed on the 60-day injured list to create room on the 40-man roster for outfielder Duke Ellis, who was picked up off waivers from the Seattle Mariners on Monday. However, the Yankees reportedly planned to add Hamilton to the big league club when the rosters expand Sunday.

Manager Aaron Boone said Saturday he does not know which players the team will call up with the roster expansion.

No further information was available Saturday about what's next for Hamilton.

The Yankees expected to use Hamilton to take some pressure off closer Clay Holmes in a bullpen that has been inconsistent in recent months. The anticipation of Hamilton's return may have influenced Yankees general manager Brian Cashman's decision not to go after a top-tier reliever at the trade deadline.

Hamilton himself has had an inconsistent season, largely due to the lat injury plus a stint on the seven-day COVID-19 injured list in May. He's 0-1 with a 4.55 ERA in 29 innings pitched over 27 appearances, all out of the bullpen.

Originally selected by the White Sox in the 2016 MLB draft, Hamilton is 4-5 with a 3.52 ERA in 81 career games (three starts) with Chicago (2018, 2020), the Minnesota Twins (2022) and the Yankees (2023-24).