That was sufficient for Bonderman (10-1) to win his 10th game, giving him the highest win percentage in the league. It's his fourth straight double-figure-win season. He's well within range of his career-high 14 victories. Bonderman allowed six hits and three runs in his seven innings. He threw 87 pitches, 62 for strikes.
"Sheff has been incredible for us," Bonderman said, "not just his homers, but his presence in the lineup and his ability to get on base and give guys behind him the chance to drive in runs."
Many of those runs have come in Bonderman starts. Entering the game, the Tigers were averaging 7.47 runs per nine innings in his starts.
"These guys are putting up some runs behind me. I just have to go out and give us a chance," said Bonderman, who grew up in Kennewick, Wash. "If I give us some quality innings and keep the score down, we're going to win. I feel very fortunate that I'm 10-1."
Manager Jim Leyland said one of the reasons he has been successful is because his teammates have a genuine affection for the 24-year-old right-hander.
"When he pitches, the guys feel good. When Kenny Rogers pitches, they feel good. When Justin Verlander pitches, they feel good," Leyland said. "When players feel good about a guy, I think that's a big lift. That's a [heck] of a compliment to the pitcher."
It is, Bonderman demurs, much appreciated.
"That's a huge compliment," Bonderman said. "Anytime the manager and your teammates feel good behind you, it definitely gives you that boost of energy. When I take the mound, I feel like these guys feel we're going to win.
"I think they know I'm going to go out and compete and give it everything I have. They appreciate guys who go out there and leave everything out on the field."
His appreciation also is not limited to the Tigers clubhouse.
"He's got a great slider. He hit his spots. He's good," Mariners first baseman Richie Sexson said. "He's one of the good ones in the league, so we knew we had our work cut out for us there. We just weren't able to get him into too much trouble."
The Mariners had taken an early lead on Jose Guillen's second-inning home run, his 11th. But a hit batsman, a walk and a single set up Sheffield in the third. His towering shot seemed to float out on a pillow of air over the left-field wall. It was his 22nd home run this season and his 12th career grand slam, the first since Sept. 27, 2005, against Baltimore.
"He left something out over the plate," Sheffield said.
Sheffield had addressed the media for about 20 minutes before the game on comments he made on an upcoming HBO show, but he put all that aside, took the field and cracked a grand slam.
"I'm a professional when I step on the field," Sheffield said. "I put all the distractions -- or what people call distractions -- behind me. Between the lines, I'm all business."
Brandon Inge added a sixth-inning RBI single and Sean Casey hit a seventh-inning solo home run.
Todd Jones picked up his 23rd save, although he allowed a couple singles and had to face the tying run -- pinch-hitter Ben Broussard -- at the plate. But he struck out Broussard to end it.