Three pitches in, Porcello got two-time batting champion Ichiro Suzuki on a groundout to short. That was followed by two more groundouts in a nine-pitch first inning, and the Tigers were on their way to a 3-2 victory.
"Today, they had some choppy ground balls, not real hard ones," Leyland said. "That's a good sign. That means his sinker is dying a little bit."
Of the 20 outs recorded in 6 2/3 innings, Porcello (1-2) got 10 on infield grounders. They came off his sinker. He also had six strikeouts, most off his changeup.
"When they're taking swings like that and they're driving it into the ground, I know that day I have a pretty good sinker," Porcello said. "That kind gives me a little leeway to throw it a little more often instead of trying to come in on certain guys. I felt like my sinker was good today and had some good late movement to it."
Porcello held the Mariners to one run and four hits but ran into trouble in the seventh, yielding his first walk of the game to Luis Rodriguez along with two wild pitches. Ryan Perry struck out Jack Wilson to end the inning, and Joaquin Benoit worked a routine eighth.
Jose Valverde took over in the ninth and yielded a leadoff home run to Adam Kennedy, the first he had allowed in eight appearances. Michael Saunders hit a one-out double moments later, before Valverde struck out pinch-hitter Milton Bradley and Carlos Peguero for his fifth save.
The Tigers took two of three from the Mariners and finished 4-3 on a West Coast swing.
"It was a big game for Ricky and a big game for us," Leyland said. "We didn't win too many road trips last year. Hopefully, this will be the start of something good for us on the road."
Detroit has won six of its last nine games after a slow start to the season, while the Mariners lost for the sixth time in eight games.
Leyland played Raburn at second -- later switching him to left field -- just to keep his bat in the lineup.
"He got one on the board for us early," Leyland said.
It was also appreciated by Porcello, giving him an enhanced comfort level against a team that had scored 13 runs against the Tigers on Tuesday night.
Cabrera drove in Austin Jackson in the third with a two-out single to make it 2-0. It was Cabrera's 19th RBI in 27 games against the Tigers.
The Mariners got one back in the third on Suzuki's two-out single to right.
The Tigers added another two-out single in the fifth by Boesch, this time driving in Raburn and making it 3-1. Boesch is hitting .405 with nine RBIs in 12 road games.
The critical point for Porcello was the Mariners' fourth. The first two batters singled. He then struck out Saunders, Luis Rodriguez flied out to left and Peguero struck out.
"That was their big push. To come out of that with no runs, that was big," Porcello said. "Then we come out and scored a run [in the fifth]. That's what I have to do to be successful, establish my sinker early, use my off-speed in to lefties to keep them off-balance."
For Leyland, the critical point was two outs in the seventh with a runner on third. He brought in Perry, who is just off the disabled list, and he struck out Wilson.
"That was a huge out. It changed things around," Leyland said. "People don't realize how much that changes things. What it meant is [No. 9 hitter Chris] Gimenez will come up next inning, not Ichiro. Ichiro is tough to keep off base. That's big."
Bedard went just five innings, throwing 95 pitches, for his fourth straight loss. He walked five, two of which would score.
"Just a step forward," said Bedard, who has had three surgeries on his left shoulder. "Hopefully, next time I get through six innings."
RHP Jeremy Bonderman visited the Tigers clubhouse before the game. The appearance of the 28-year-old free agent sparked speculation that he might be interested in returning to the Tigers. Bonderman lives in Kennewick, Wa. ... Mariners RHP David Aardsma, on the DL after hip surgery, had his first rehab assignment Tuesday. He threw 22 pitches, allowed two hits, including a two-run home run, and walked two. "I felt good, being on the mound, facing hitters and getting that anxiety out of the way," said Aardsma, who will throw again Friday. ... Peguero, called up Tuesday to replace Justin Smoak on a bereavement leave, made his big league debut as a ninth-inning defensive replacement. He started in left field and was 0 for 4.