FOXBORO — The Patriots made an under-the-radar late-season addition before Thursday night’s 21-18 win over the Steelers when they put in a waiver claim for ex-Eagles linebacker Christian Elliss.

The move became official Friday when the Patriots waived running back/wide receiver Ty Montgomery to add Elliss to the roster.

Belichick explained Wednesday why the Patriots wanted to work with Elliss.

“We’ve seen him, played against him earlier in the year, kind of followed him through the year,” Belichick said. “Depth at linebacker is always something you’re always looking for, every team’s looking for, especially at this time of year. So, I had an opportunity to get it. Look forward to working with him.”

Elliss has been a core special-teams player for the Eagles for two seasons. He actually started the Eagles’ Week 13 loss to the 49ers before being waived.

The third-year pro, who entered the NFL as an undrafted free agent out of Idaho in 2021, will be an exclusive-rights free agent after the season, which makes him easy to retain for the 2024 season.