Valverde, 35, signed a minor league deal with Detroit in April and briefly returned to the team earlier this season. He went 9 for 12 in save chances with an ugly 5.59 ERA and 1.24 WHIP in 19 1/3 innings. The Tigers removed him from the roster in June.
In 11 games with the team's Triple-A affiliate, Valverde saved seven games with a 4.09 ERA in 11 innings. He also made three tuneup appearances with the club's Single-A affiliate in Florida after signing.