MLB: Oakland Athletics at Boston Red Sox

Former Red Sox pitcher Tyler Thornburg, right, celebrates with Mookie Betts after a May win at Fenway Park.

The Red Sox had high hopes for Tyler Thornburg when they traded for him in 2016, and though injuries derailed him, the team was optimistic he could be effective coming into this season.

But his tenure in Boston just never came together.

The Red Sox on Wednesday cut ties with the right-handed reliever, officially announcing they have released Thornburg. It came just a day after he refused a minor league rehab assignment, according to WEEI.com.

Thornburg missed the entire 2017 season after he underwent thoracic outlet syndrome surgery. He returned midway through last season and showed flashes of what the Red Sox had hoped for, and was re-signed to a one-year deal after the season.

But Thornburg struggled in 2019. He posted a 7.71 ERA in 16 appearances before being placed on the injured list with a right hip impingement. His struggles continued during a rehab assignment with Triple-A Pawtucket.

The 30-year-old Thornburg finished his Red Sox career with a 6.54 ERA in 41 appearances.

After a strong 2016 season in Milwaukee, Thornburg came to the Red Sox in a deal that sent Travis Shaw, Mauricio Dubon and three other minor leaguers to the Brewers.