PITTSBURGH, Pa. - Jordan Zimmermann is making $110 million look like a wise investment. Maybe even a bit of a bargain.

The centerpiece of Detroit's off-season pitched six shutout innings as the Detroit Tigers pulled away from the Pittsburgh Pirates 7-4 on Thursday.

Zimmermann, who signed a five-year deal to spearhead the front of Detroit's rotation, allowed six hits, striking out four and walking two to improve to 2-0 and has yet to see an opponent cross home plate through his first 13 innings on the mound for the Tigers.

"He hasn't given up a run so in that sense I guess he's better than advertised," Detroit manager Brad Ausmus said. "We expected him to give up a run."

Zimmermann nearly did, loading the bases in the first and the fifth before wriggling free both times. Josh Harrison grounded into a force out to end the first and Zimmermann worked his way back from a 3-0 count against Gregory Polanco in the fifth to induce a shallow pop behind second.

While not the tidy seven innings of two-hit ball he tossed in his debut against the Yankees last week, Zimmermann didn't lose his composure has he battled traffic on the bases.

"You've just got to tell yourself to stay calm," he said. "I've been in those jams many times over the years. You just make your pitch at that point and hope for the best.

Nick Castellanos went 3 for 4 with a home run and four RBIs for the Tigers, who improved to 4-0 away from Comerica Park while taking the final three games of the four-game interleague set with the Pirates.

Castellanos hit a two-run double in the fourth off Gerrit Cole (0-2) and added a two-run homer in the eighth off Tony Watson. Francisco Rodriguez pitched a perfect ninth for his second save.

"I'm seeing the ball well," Castellanos said. "I'm still sometimes expanding but it's still early and the only thing I can do is try to get better."

CLOSE CALL

Cole gave up two runs in six innings, striking out five and walking one in a marked improvement over a bumpy 2016 debut last weekend against Cincinnati. The Pittsburgh ace also survived a scare in the sixth when a liner from Zimmermann glanced off his head. The ball grazed off Cole's cap and into centre field. He remained on the ground for several moments while getting checked out but stayed in the game.

"I hit the deck pretty hard," Cole said. "I was just trying to get out of the way."

Pirates manager Clint Hurdle said Cole was "coherent" while responding to assistant trainer Ben Potenziano.

"Answered every question, looked us in the eye," Hurdle said. "All the things Ben asked him to do he was able to do and all the questions, he answered. "

BUMPY BULLPEN

Pittsburgh's typically reliable bullpen is going through a rough stretch, giving up 15 runs in 12 innings to the Tigers in the final three games of the series.

Tyler Collins hit an RBI double and Bobby Wilson hit a sacrifice fly off reliever Rob Scahill to put the Tigers up 4-0 in the seventh. Pittsburgh drew within one after Zimmermann exited, tagging Drew VerHagen for three runs in the seventh. Detroit responded immediately thanks to a rare shaky outing by Watson.

J.D. Martinez's sacrifice fly made it 5-3 and Castellanos followed with a shot a few rows deep into the sun-splashed bleachers in left field at PNC Park.

TRAINER'S ROOM

Tigers: Pitcher Blaine Hardy will continue his rehab from a left-shoulder impingement at Triple-A Toledo. Hardy, who has been on the disabled list since March 25, allowed posted a 6.00 ERA with six strikeouts in two appearances for Class A Lakeland. ... OF Cameron Maybin, recovering from a fractured left wrist, is hitting just .143 on his rehab assignment with Toledo.

Pirates: Put left-handed reliever Cory Luebke on the 15-day disabled list with tightness in his right hamstring and recalled Scahill from Triple-A Indianapolis. Luebke, who made the team as a non-roster invitee to spring training, is back in the majors for the first time since 2012 after going on a pair of Tommy John surgeries on his left elbow. Luebke has an 8.10 ERA in three appearances.

UP NEXT

Tigers: Detroit heads to Houston for a three-game set on Friday. Mike Pelfrey will look for a better outing than his 2016 debut, when he gave up six runs in 3 2/3 innings against the Yankees.

Pirates: Pittsburgh opens a three-game series against Milwaukee on Friday. Jeff Locke will make his second start of the season for the Pirates. Locke allowed one run in six innings last Sunday in Cincinnati. The 28-year-old is 5-4 with a 3.75 ERA in 12 starts against the Brewers.