Porcello (1-2) raised his career record to 3-0 against the Mariners with a strong performance Wednesday. He surrendered four hits and one walk to go with six strikeouts as the Tigers took the rubber match of a three-game series against Seattle.
The Detroit closer yielded a lead-off homer to Adam Kennedy, allowing the Mariners to pull to within a run. Mike Saunders then added a one-out double before Valverde fanned Milton Bradley and Carlos Peguero to end the game and notch his fourth save.
Ryan Raburn hit a solo homer while Magglio Ordonez and Miguel Cabrera added RBI for the Tigers.
Mariners starter Erik Bedard (0-4) allowed three runs on five hits over five innings.