McCullers was on the mound for all five homers as the Phillies claimed a 2-1 World Series lead at a rowdy Citizens Bank Park. He became the first pitcher in postseason history to allow five home runs in a game.
The Astros starter gave up a walk and three homers in the first two innings, but rallied to retire seven batters until blasts from Kyle Schwarber and Rhys Hoskins saw him pulled with the Phillies in an unassailable position in the fifth inning.
"I got beat, man," McCullers told reporters. "They hit a lot of solid pitches, I thought.
"At the end of the day, we got beat pretty bad, and I got beat up pretty bad."
The five homers came four types of pitches, with two sliders, a change-up, a curveball and a sinker, but nothing worked for McCullers.
"Listen, I am who I am," McCullers said. "I'm going to throw a lot of off-speed. Everyone knows that."
The Phillies had come up against McCullers late in the regular season, when he gave up six hits but only one earned run, yet they seemed to know what was coming this time.
"He's a guy that we saw at the end of the year in Houston," Phillies catcher J.T. Realmuto said. "Got to see his pitches then. He just left pitches in the middle of the plate today."
Bryce Harper, who delivered a two-run blast in the first inning, added: "We talked about it before the game, just trying to get on him early, trying to get on him often."
Seven-time All-Star Harper, who is a two-time NL MVP, along with Rhys Hoskins have six homers this postseason which is the second most in franchise history. Harper is also hitting at .382 this postseason.
"I'm just so focused on winning," Harper said. "I'm not focused on anything else besides that. Just having the opportunity to come in here and grateful for the opportunity to be here. Just grateful to be here with this team and this organisation. I'm not really worried about anything else."
The Phillies are 6-0 at home this postseason cheered on by their boisterous fans, having blasted 17 homers in those games too, with Game 4 at Citizens Bank Park to come on Wednesday.
"Just walking into the ballpark, just being back home, I think is such a momentum swing for us," Harper said. "We all come in here and we're ready to go and we're excited to get on the field, because we know they're going to show up and there's going to be 46,000 people here screaming and yelling and going crazy."