Grilli came into the game in the bottom of the 11th inning with the Pittsburgh Pirates clinging to a 1-0 lead and the heart of Detroit's order -- Torii Hunter, Miguel Cabrera and Prince Fielder -- awaiting him.
"That's as good as it gets in any lineup in the game," Pirates manager Clint Hurdle said. "That's why you have a closer."
For Grilli, it also meant trying to finish a game at Comerica Park -- a stadium where he had been booed relentlessly at the end of his four-season stint with the Tigers.
"I have nothing but great memories of this place," Grilli said. "This is where Jim (Leyland) turned me into a reliever, and despite what the media might think I love coming back here."
If the situation or the setting bothered Grilli, it certainly didn't show. He struck out Hunter, Cabrera and Fielder in order, ending the game as the clock approached 11:30 p.m.
"That's a great offense, and Miguel Cabrera is probably the best hitter in baseball right now," Grilli said. "So I was trying to not make a big mistake, but you can't spend much time thinking about that. You just go out there and win the game."
Grilli certainly impressed the first of his victims while posting his 21st save in as many chances.
"I faced him when I was in Minnesota and he was here in Detroit, and he's a different pitcher now," Hunter said. "He's smart and he's got a little deception going. He jumps out at you, and before you know it, the ball is gone."
Leyland knows just how far Grilli has come since moving to the bullpen in 2006.
"He's found a home and he's found a role and he's been terrific," he said. "That's 21-for-21, and to do that against the heart of our order -- that's impressive."
"I was just feeling really good today," said Gomez, who threw only 73 pitches. "Every one of my pitches was working, so I was working ahead in the count and down in the zone. That's what made it good."
"I've been swinging the bat really well on this road trip, and I've been getting the barrel on the ball just about every night," Walker said. "That kid throws hard, but he kind of floated a slider into the strike zone and I was able to drive it."
Mark Melanson (1-0) picked up the win with a scoreless 10th inning for Pittsburgh.
Porcello also matched a career best with his eight innings and struck out a career-high 11 batters. Porcello isn't the first Tigers pitcher to dominate Pittsburgh at Comerica Park. Last season, Justin Verlander took a no-hitter into the ninth against the Pirates, two days before Max Scherzer struck out 15 batters in a 4-3 victory.
"Someone said to me today that we seem to strike out a lot in this ballpark," Hurdle said. "I told them to look at Detroit's pitching staff. Everyone strikes out a lot against those guys."
Pedro Alvarez led off the eighth with a single and took second when Travis Snider walked -- the first time either team had put a runner into scoring position -- but Porcello got Clint Barmes to ground into an inning-ending double play.
In the bottom of the inning, Omar Infante got to second on a one-out throwing error by Barmes at shortstop. Reliever Justin Wilson retired pinch-hitter Brayan Pena on a ground ball, and struck out Dirks.
Walker singled off Joaquin Benoit in the ninth, stole second and took third on Pena's throwing error, but Garrett Jones flew out to end the threat. Victor Martinez almost ended the deadlock in the bottom of the ninth, but Starling Marte made a running catch of his liner at the fence in left.
Both teams put runners into scoring position in the 10th, but couldn't get a run across until Walker's no-doubt homer in the 11th.
"We had chances in the eighth, ninth and 10th, but we couldn't get the big hit," Hurdle said. "We finally got that in the 11th."
The start of the game was delayed 1:13 by rain. ... The Pirates placed Jose Contreras (low back inflammation) on the 15-day disabled list and recalled reliever Bryan Morris from Triple-A Indianapolis. ... The Tigers have struck out 10 or more batters 28 times -- the second-highest total in franchise history behind last season's 50. Detroit is currently on pace for 91 double-digit games. ... Porcello pitched into the ninth on July 21, 2012 against the White Sox, but didn't record an out.