The Braves closer, making his return to the PNC Park mound, allowed the game-winning run in a 3-2 loss to the Pirates in 10 innings.
For a guy who bought a house in Pittsburgh this offseason, it wasn't an ideal welcome back for the 38-year-old right-hander.
"It's unfortunate it was here," Braves manager Fredi Gonzalez said. "But he's the type of guy that if you run him out there tomorrow, he'll close a game out for you."
The frame started with Andrew McCutchen -- Grilli's former teammate who lives "just up the road" from him. First-pitch swinging, McCutchen roped a double to left field on a 94-mph fastball.
"McCutchen knows my style. I'm trying to get ahead. He was aggressive," Grilli said. "I didn't want to walk a guy. He earned it."
After intentionally walking Starling Marte and striking out Pedro Alvarez, it was Pirates shortstop Jordy Mercer who doubled to the Clemente Wall in right to score McCutchen for the walk-off.
Pirates manager Clint Hurdle said familiarity with Grilli helped a little bit. The Syracuse, N.Y., native spent three-and-a-half seasons in a Pittsburgh uniform before being traded midseason to the Angels in 2014.
During that period of time, Grilli was a crucial part of the 2013 Pirates -- the first Pirates team to make the playoffs since 1992. He was also an All-Star.
But that past insight into Grilli's tendencies can and will only go so far. There's still the application of prior knowledge, which McCutchen and Mercer were successful in doing.
"We know Jason," Hurdle said. "You're going to get a fastball. You've got a good chance of getting a breaking ball…Cutch was able to touch him up first pitch, and Jordy was able to stay in the at-bat and get that ball up out over the plate and drive it."
Grilli said pregame that he hoped for a warm welcome, which, for the most part, he received from the PNC Park crowd. The closer, who has 20 saves with the Braves this year, appreciated the fans' past and present support.
"Everyone to this day still say, 'Man, we miss you here. Thanks for everything you did.' It feels good," Grilli said pregame.
But he knew entering Friday night's game that his former teammates -- still his friends -- were the enemy.
"I'm wearing a Braves uniform," Grilli said at the time. "I want to have bragging rights against my old buddies."
For now, those old buddies have the advantage.
John McGonigal is an associate reporter for MLB.com.