With the loss, the Padres (71-80) were eliminated from postseason play.
To be sure, it's been a vexing season for Stults (7-17), who scuffled in the first half but had pitched much better since the All-Star break, posting a 3.66 ERA in his last 10 starts going into Wednesday.
Stults allowed a leadoff single to Ben Revere and then set down the next 12 hitters before the bottom fell out in the fifth inning, as the first four Phillies (70-82) reached base on singles, including a two-run poke up the middle by Freddy Galvis for a 2-1 lead.
"Four sharp innings then some balls found some holes," said Padres manager Bud Black. "Some sharp-hit grounders, but a bunch of singles. You look at the line and it will say four runs in four and a third … but I thought he threw the ball well."
After a sacrifice bunt by pitcher Cole Hamels -- who did better things with his left arm -- Revere followed with a two-run double for a 4-1 lead. One minute, Stults was rolling. The next, he was reeling.
"It happened pretty quickly," Stults said. "It was just one of those innings where some balls found some holes. I didn't execute pitches quite as well. There was probably some good hitting on their part, too. It just didn't go my way."
That wasn't the case for his counterpart, though.
Hamels, the San Diego native, improved to 9-2 in 16 career starts against the Padres by allowing one run on seven hits over seven innings. He walked one, struck out nine and also lowered his ERA to 2.47.
"He's awfully tough," Black said. "He's not third in the league in ERA for nothing. He's getting better."
The Padres had some hard contact at times against Hamels, like in the fourth inning when they got to him for a run as Tommy Medica had the second of his two singles, stole second base and then scored when Cameron Maybin singled to center field.
"We ran some good at-bats up there and hit some balls hard right at someone. What did we have, nine hits? It seemed like we had guys on base but then they just sort of disappeared," Medica said.
That can happen when Hamels is pitching, especially in his native San Diego, where he's now 5-1 at Petco Park.
"He's been solid, even when he's not at his best," said Phillies manager Ryne Sandberg. "He was behind in the count a lot of the game, especially the last three innings. But his changeup was real effective when he was behind in the count. He seems to find a way. He has a lot of weapons. Something usually works, if not everything."
The Padres got a run in the ninth inning off reliever Ken Giles as Alexi Amarista knocked in Maybin, but that was as close as the game got.