Seager doubled off Rodriguez with one out in the ninth, and Gamel followed with an RBI single to right-center field in the Mariners' 2-1 victory Thursday.
"Kyle had a great at-bat, and I got a good look at what K-Rod was throwing." Gamel said. "I knew he was going to throw me a changeup on 2-2, and that's what I got."
Rodriguez (1-2) has a 6.23 ERA in nine games this season.
"You saw exactly what happened," he said. "I couldn't get anybody out and it cost us the game."
The Mariners closed the series with two one-run victories after falling 19-9 in the opener.
Detroit starter Justin Verlander allowed one unearned run on five hits and two walks in seven innings. He struck out eight after allowing 13 runs in his past two games.
"I knew right out of the gate that my arm felt cleaner than it has in the last couple starts," Verlander said. "Everything was coming out better. I made an adjustment a couple starts back and it clicked today."
Seattle starter Hisashi Iwakuma gave up an unearned run in 5 2/3 innings. He allowed three hits and a walk and struck out three.
"There were obviously two great pitching performances going out there," Seattle manager Scott Servais said. "Verlander was outstanding, but Hisashi matched him."
Seattle broke a scoreless tie in the sixth. Nelson Cruz reached when center fielder Tyler Collins was given a two-base error for running into Jim Adduci as the right fielder was about to catch a routine fly ball. Seager followed with an RBI single for the first run.
Mariners: RHP Steve Cishek (hip) is scheduled to pitch an inning for Double-A Arkansas, marking the first time he has pitched back-to-back days during his recovery process. Cishek hopes to return to Seattle's bullpen in early May.
Tigers: SS Jose Iglesias was activated from the concussion list before the game, and LHP Kyle Ryan was optioned to Triple-A Toledo. Ryan posted a 7.94 ERA in eight relief appearances, allowing nine hits and seven walks in 5 2/3 innings. ... Adduci left the game after eight innings when his calf tightened up after the sixth-inning collision with Collins.
K-ROD CAN'T SOLVE LEFTIES
The ninth inning saw Rodriguez continue to struggle against left-handed hitting. After Seager's double and Gamel's single, lefties are hitting .385 with a .429 on-base percentage and .846 slugging percentage in 28 plate appearances against the Detroit closer.
"I'm extremely disappointed," he said. "I'm just missing my spots. I've got to pitch better and quickly start getting people out."
MARINERS PITCHING REBOUNDS
After allowing 19 runs in the series opener and losing Felix Hernandez to a stiff shoulder, Seattle outscored the Tigers 10-1 in the final two games. James Paxton threw seven shutout innings in Wednesday's 9-0 win before Iwakuma's strong outing on Thursday.
"We all have to step up to replace Felix," Iwakuma said through an interpreter. "That's what we did the last two days."
Tigers: LHP Matthew Boyd (2-1, 3.86) takes on former teammate Mike Pelfrey (0-1, 4.15) as the Chicago White Sox visit Detroit for a weekend series. Pelfrey was released by the Tigers this spring despite being owed $8 million in the last year of his contract.
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