Contreras signed a minor-league contract with the Red Sox on Friday, Matt Eddy of Baseball America reports.
Contreras was released by the Twins on Thursday, Brandon Warne of Access Twins reports.
Contreras was designated for assignment by the Twins on Tuesday, Brandon Warne of Access Twins reports.
Contreras was recalled from Triple-A St. Paul on Friday, Brandon Warne of Access Twins reports.
Contreras was optioned to Triple-A St. Paul on Saturday.
Contreras went 1-for-3 with a solo home run in Tuesday's 5-3 loss to the Tigers.
The Twins optioned Contreras to Triple-A St. Paul after Sunday's 3-2 loss to the Padres, then recalled him ahead of Monday's game against the Tigers.