Chavez (3-6, 2.75) allowed one run on three hits in seven innings, and he got the run support he's been deprived of most of the season.
"Yeah, I was telling Jess after the game, I said, 'We can't score for you, then we put up 16,'" Billy Butler said. "Kind of feel they came all at one time. He's pitched great all year and just had some tough luck."
The right-hander entered the game with the lowest run support in the Majors. Despite his impressive ERA, he had just two wins on the season and was rarely rewarded for his efforts.
That all changed Wednesday, as the A's exploded for 20 hits. Chavez was prepared to continue pitching in the eighth, but the A's tallied seven more runs to turn a blowout into a massacre.
A's manager Bob Melvin said it was right up there with the best performances he's seen from Chavez, adding that his changeup was the main reason for his success against the Padres.
Melvin said catcher Stephen Vogt called for the changeup early, and once it worked he kept turning to it. Having an off-speed pitch as a legitimate threat -- even to righties -- paid huge dividends.
"This was the best changeup we've ever seen him throw," Melvin said, "and he threw a bunch of them tonight."
Chavez struck out the side in the first and fanned at least one batter in every inning. He said he wasn't focused on his strikeout total and was unaware he had a career high.
"I just want to end the at-bat as quick as I can," Chavez said. "That allows a pitcher to go deep in a ballgame."
That's what he did, pitching at least six innings for the eighth time in his last nine starts. The mood in the A's clubhouse was one of joy, but also one of relief.
They finally got Chavez some support, scoring at least four runs in one of his starts for just the third time this season. The A's had scored 22 runs in Chavez's previous 10 starts.
"He pitches so well every time, and we just haven't put up the runs for him," Billy Burns said. "It was really nice to pay him back a little bit."
Trevor Hass is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.