"To get a win on your birthday, that's an awesome feeling," Hahn said, beaming. "It makes it a lot easier when they put up runs like that."
The Padres (48-59) were already up, 4-1, before batting around -- and then some -- to send the Cardinals fans in attendance to the exits.
Jeff Francoeur grounded out to lead off the seventh, but by the time he came up again, every Padre had reached and scored. Jedd Gyorko had a bases-clearing double and Will Venable bookended the offensive outburst with a three-run homer.
"It was probably our ugliest loss of the year," said Cardinals manager Mike Matheny. "That's the best way to describe it."
San Diego certainly didn't resemble the Majors' worst offense on this night. In fact, they've scored the most runs (59) among all National League teams since the All-Star break.
"We're seeing better at-bats since the All-Star break," said Padres manager Bud Black. "A lot of good things offensively tonight. We got to continue it."
The Friars didn't exactly need such a powerful display with their rookie phenom dealing, though.
Hahn (7-2) didn't allow a hit out of the infield until Kolten Wong poked a single to left with two outs in the sixth, as one of the Cardinals' numerous grounders finally snuck through into the outfield grass.
Black and Hahn both attributed the youngster's success to excellent movement on his fastball, which often dipped like a sinker and other times tailed like a two-seamer.
"It got a lot of ground balls for me tonight," Hahn said. "The first inning I actually had trouble controlling it a little bit -- I don't think my fastball has ever moved that much."
St. Louis (56-50) finally got to him in the seventh, which Hahn entered having thrown 83 pitches. Matt Adams led off with an opposite-field double down the left-field line, and he scored later in the inning when Peter Bourjos beat out a potential 6-4-3 double play at first to keep the inning alive.
But this was Hahn's night -- he promptly picked off Bourjos to end the frame and his outing with a bang.
The right-hander gave up four hits and one run with two walks and three strikeouts in seven frames. Since being recalled on June 14, he has a 1.44 ERA in nine starts against some of the National League's best teams. His last five wins have come against the Cardinals, Braves, Dodgers, Reds and Giants.
"He's not a secret, even though he's been facing teams for the first time," Black said. "He's being talked about because he's made a number of starts and his innings are getting up there a little bit. First look for the Cardinals, I think they saw a guy with a good fastball and a good hook who mixed in some changeups as the game went on."
Hahn's seven wins through his first nine career appearances are the most in franchise history. He had plenty of offensive support Wednesday to ensure he'd set that mark.
Yangervis Solarte had the first four-hit game of his career as he continued his torrid start with the Padres. He owns a slash line of .364/.410/.606 since being acquired on July 22 in the Chase Headley deal.
Jedd Gyorko was 3-for-5 with a solo homer in the third off Joe Kelly (2-2) that gave San Diego a 3-0 lead. Gyorko is 6-for-11 in three games since returning Monday from his two-month stint on the disabled list.
"It obviously feels good to swing the bat the way I have the last few nights," Gyorko said. "It's something to build on, still got a long way to go."
Before this hot streak, Gyorko hadn't collected five hits in a three-game span this season.
"It was a tough struggle for Jedd prior to going on the disabled list, no doubt about it," Black said. "It's still early to tell, but the initial signs are pretty good the way he's swinging here."
The Padres never let Kelly get comfortable on the mound, as Alexi Amarista was a pest on the basepaths in the early going. He beat out a potential double play, stole third and scored on Solarte's single in the first. Then in the third, he scampered home on a wild pitch, sliding just under Kelly's tag to give San Diego a 2-0 lead. Kelly allowed four runs and seven hits with one walk and five strikeouts in five innings.
But he fared far better than the Cardinals' bullpen, which used three relievers in the seventh to try to stop the bleeding but could do nothing to prevent the Padres from giving their surprise phenom an appropriate birthday gift.