The teams says RHP Brayan Villarreal will be optioned to Triple-A Toledo.
Valverde was the Tigers' primary closer until he left the team at the end of last season. After not signing with with another team, he signed a minor league contract with the Tigers earlier this month.
"Valverde will be with the club in Detroit tomorrow and manager Jim Leyland says he will be the team's closer," the team tweeted Tuesday night.
The Tigers expect to make another move to clear space for Valverde on the 40-man roster.
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