Mattson signed a minor-league contract with the Pirates on Thursday, Noah Hiles of the Pittsburgh Post-Gazette reports.

The Pirates outrighted Mattson to Triple-A Indianapolis on Monday, Andrew Destin of the Pittsburgh Post-Gazette reports.

The Pirates selected Mattson was selected from Triple-A Indianapolis on Thursday, Noah Hiles of the Pittsburgh Post-Gazette reports.

Mattson signed a minor-league contract with the Pirates on Dec. 11.

The Orioles released Mattson on Monday.

Mattson (shoulder) has made three relief appearances for Triple-A Norfolk this season, covering three no-hit scoreless innings while striking out three and issuing one walk.

Mattson (shoulder) cleared waivers and was outrighted to Triple-A Norfolk on Friday, Roch Kubatko of MASNSports.com reports.

Mattson (shoulder) was optioned to Triple-A Norfolk on Wednesday, Zachary Silver of MLB.com reports.

Mattson is a month behind schedule due to shoulder soreness, Roch Kubatko of MASNSports.com reports.

Mattson was recalled from Triple-A Norfolk on Friday.