But with the game tied in the seventh inning, Frazier sent an Edubray Ramos fastball into the right-field seats to lead the Pirates to a 5-4 victory.
"It was up and in and I figured he was coming back with a fastball after just missing with two off-speed pitches," Frazier said, while noting that he got a scouting report from his time playing with Ramos in the Arizona Fall League in 2015. "I got my hands to it and got the barrel out front."
The 407-foot pinch-hit homer was not only his first bopper in the majors since being called up June 24, it also was his first at any level since Sept. 5, when he was with Double-A Altoona. He hit just three total minor-league home runs in the Pirates organization since being drafted out of Mississippi State in 2013.
"I was pretty excited to see the ball clear the fence," he said. "In a tie game, I was just trying to do whatever I can. It was pretty big."
Making his second appearance since a trip to the disabled list for a fatigued shoulder, Pittsburgh starter Jameson Taillon struck out seven batters in six innings but was also hittable at times. He surrendered four extra-base hits, including solo home runs by Odubel Herrera and Andres Blanco, which allowed the Phillies to build a 4-2 lead.
Pirates manager Clint Hurdle credited Taillon's maturity for him to allow big hits early but remain focused and effective.
"He made some mistakes and he paid for them, but he kept us in the game and he really didn't fold or go away," Hurdle said. "He stayed on the aggression throughout the outing."
The Pirates' comeback started in the sixth inning, when Starling Marte lead off with a double to center and Matt Joyce sent a first-pitch fastball from Philadelphia starter Vince Velasquez 434 feet off the batters' eye beyond the centerfield wall.
The home run was the 10th of the season for Joyce, his most since 2013 despite only having a part-time role. He is slugging a career-high .563 on the season, after posting a career-low .291 mark in 2015 with the Anaheim Angels.
"I felt (when we got him) we got a good, plum ballplayer that could bounce back and have a good season," Hurdle said. "I didn't think about numbers. Obviously, these are eye-catching numbers. He's leading the team in home runs at home. In the role he's playing, that's pretty impressive, as well. Good for him. He's worked hard and this is part of the game you love as a coach."
Joyce also walked and scored as part of the Pirates' two-run second inning. Marte led off the inning with a single and Elias Diaz drove him in with a groundout to record his first career RBI. Sean Rodriguez then drove in Joyce with a double to center.
The Phillies scored a pair off Taillon in the third when he gave up a leadoff single to Velasquez. Cesar Hernandez drove in Velasquez with a triple off the wall in center field and then came around to score on Herrera's groundout.
Mark Melancon pitched the ninth inning to record his 30th save, the third most in the National League. He became the first Pirates pitcher to have three consecutive seasons with 30 or more. He led the big leagues with 51 saves in 2015, and his 114 saves since the start of 2014 are the most in the majors.
Ramos took his first career loss to fall to 1-1. Frazier's homer made a winner of Pirates' reliever Neftali Feliz, who is 4-0.
The game was delayed an hour and 32 minutes by a thunderstorm in the bottom of the eighth inning.
Phillies: Blanco left the game with a fractured left index finger after applying a tag on Gregory Polancoat third base in the fifth inning. Polanco was attempting to steal third. Blanco took the throw from catcher Carlos Ruiz in plenty of time and tagged Polanco, who contacted Blanco's glove with his foot. Blanco was replaced by Maikel Franco. It was Franco's first action since being removed from Friday's game after being hit by a pitch in his wrist. He went 1 for 2 at the plate. ... Catcher Cameron Rupp did not play as a precaution after being hit in the head with a pitch Saturday. Concussion tests done Saturday night and before the game Sunday were negative.
Pirates: Right-handed pitcher Tyler Glasnow was placed on the 15-day disabled list before the game with right shoulder discomfort.
Phillies: Jeremy Hellickson (7-7, 3.84 ERA) will start a three-game set in Miami. In his last seven starts, he's walked just seven batters and has a 0.98 WHIP while lowering his ERA by half a run. The Phillies enter the series 9 1/2 games behind the Marlins for the final NL Wild Card spot.
Pirates: Francisco Liriano (6-9, 4.96 ERA) will begin a two-game series against the Seattle Mariners after an off day Monday. The Pirates have rearranged their starting rotation to keep Liriano and Gerrit Cole on as close to five days of rest as possible during a stretch where they have four days off in a three-week span.