DETROIT -- Bruce Rondon is big.

Big body, big fastball, big slider and big changeup. But the Detroit Tigers are eager to find out whether he can be a big closer as well.

With current closer Alex Wilson unavailable due to arm and shoulder fatigue, Rondon pitched a workable four-batter ninth inning Saturday night to preserve a back-and-forth 7-6 victory for Detroit over the Boston Red Sox.

A two-out, two-run home run by designated hitter Victor Martinez in the seventh inning regained the lead for the Tigers, and left-hander Blaine Hardy and the 6-foot-4, 250-pound Rondon closed it out.

"It's big for us, too, not just for him," said Tigers manager Brad Ausmus, who has been plagued by bullpen problems all season.

But Rondon is the kind of pitcher who can intimidate and set up the back end of a bullpen. His fastball reaches and exceeds 100 mph. What has made him successful recently is that catcher James McCann is calling for sliders and changeups in put-away counts. Rondon has been getting them over for strikes and causing swings and misses.

"He's got a different look, a different look in his eye," Ausmus said. "He looks confident. He's attacking hitters with his fastball. He's not trying to trick them. He's going right at them. He did a very good job, and he pitched intelligently, too."

Rondon got two quick outs in the ninth, walked designated hitter David Ortiz on a 3-2 slider then slipped a 1-2 slider past third baseman Pablo Sandoval for a game-ending third strike.

Martinez hit two home runs Thursday, and his shot into the right-field seats Saturday off right-hander Junichi Tazawa (2-5) was his ninth of the season. It followed a two-out single by second baseman Ian Kinsler.

"Left-handers are obviously getting good swings off (Tazawa)," Red Sox manager John Farrell said. "Martinez hit a split-finger that was up. He hasn't pitched in five days; but, the last few times he's pitched, he hasn't been as sharp.

"He's throwing his fastball away, but he's been pulling it back to the middle of the plate."

Hardy (4-2) relieved starting right-hander Alfredo Simon with the bases loaded, two outs and Detroit clinging to a 5-4 lead in the seventh. An RBI single to third by right fielder Rusney Castillo off Simon had cut a run off the Tigers' 5-3 lead.

Ortiz, who earlier had doubled and hit a solo home run, grounded a fat 1-2 fastball up the middle for a two-run single off Hardy that put Boston back on top, 6-5. Hardy gave up two hits and a walk while getting four outs to gain the win.

"They're obviously pitching very carefully to him," Farrell said of Ortiz, whose $11 million option for 2016 triggered when he stepped to the plate in the second inning. "But when he does get his pitch, he's not missing it. He's in a groove, clearly locked in."

He scored on a sacrifice fly by first baseman Travis Shaw in the second and broke a 2-2 tie with his 23rd home run of the season, a solo shot to deep right in the sixth.

Kinsler went 3-for-4 and scored twice for Detroit (54-56), and catcher James McCann also had three hits. Left fielder Rajai Davis hit a two-run home run, his third homer of the season.

Catcher Blake Swihart went 3-for-4 and scored twice for Boston (49-62).

NOTES: Boston LF Hanley Ramirez, who has been battling various ailments, was a late scratch. He was replaced by LF Alejandro De Aza and manager John Farrell said Ramirez was doubtful for Sunday. ... Detroit C James McCann, involved in a dugout dustup Fridaywith SS Jose Iglesias, is showing leadership qualities, according to manager Brad Ausmus. "Above all else, he cares about the team, his teammates and winning more than he cares about himself," Asmus said. "Those are pretty much the qualities you want." ... The Red Sox called up INF Deven Marrero from Triple-A Pawtucket to fill the vacancy created by the trade of 1B Mike Napoli to Texas. Marrero, called up briefly earlier this season, was hitting .237 in 78 games with Pawtucket.