The Phillies added another element to their bullpen reconstruction Monday when they claimed right-handed reliever Trevor Kelley off waivers from Boston.

Kelley, a 26-year-old sidearmer, reached the majors last July after being a 36th-round pick in 2015. He has minor-league options remaining, meaning the Phillies could rotate him next season between triple A and the majors.

Kelley was excellent last year in triple A, where he had a 1.72 ERA in 52 appearances and limited left-handed hitters to a .117 batting average.

But he struggled with the Red Sox. Kelley posted a 8.64 ERA in 8 1/3 innings, allowing an earned run or an inherited runner to score in six of his 10 appearances. He throws a high-80s, sinking fastball as well as a slider and cutter.

The Phillies claimed hard-throwing Robert Stock off waivers in October from San Diego. They parted with six relievers — Pat Neshek, Tommy Hunter, Blake Parker, Mike Morin, Edubray Ramos, and Jared Hughes — after the season.

Rebuilding a bullpen that finished last season with the National League’s eighth-best ERA is a focal point of the offseason, and key additions could come at this month’s winter meetings.