The 5-4 series-opening victory over the White Sox is the A's season-high fifth straight, coming on the heels of a three-game sweep of the Nationals, and their 24-15 record is their best after 39 games over the last 24 years.
It's also the highest win total in the American League.
Chavez was superb, allowing a solo home run to Dayan Viciedo in the second inning but just four other hits on the night -- the last a leadoff home run to Jose Abreu in the ninth that would mark the end.
Still, the eight innings are a career high for Chavez, who struck out seven next to just two walks while needing only 93 pitches. The right-hander recorded 19 outs with three pitches or fewer, all the while lowering his ERA to 2.44, which ranks seventh in the AL.
"It's what he's been doing all year for us, basically," said manager Bob Melvin. "He had a great cutter to both sides of the plate, slows them down with the curveball, had a good changeup at times tonight. I tried to get him all the way through it, and obviously that didn't happen, but, man, eight strong -- again, it seems like he's been consistent as his numbers are.
"He throws the ball where he wants to. He's focused and taking advantage of this opportunity."
"That's probably the best I've felt all year, just staying focused and ahead of the count and mixing everything," Chavez said.
Getting him the win wasn't as easy.
Following Chavez's departure, Fernando Abad walked his only batter, and Jim Johnson proceeded to give up a run on back-to-back hits, forcing Melvin to go to Sean Doolittle.
The southpaw allowed a sacrifice fly to pinch-hitter Paul Konerko to narrow Oakland's lead to one. But he would strike out his final two batters.
"In situations like that, you can't look at the bigger picture of coming in to get the save," said Doolittle. "You have to really break it down to one pitch at a time. You have so many things going on, runners at the corners, Konerko at the plate, you have to focus on making a quality pitch right from the start. Getting that first out was really big."
Chicago still leads the AL in runs with 201, but the A's aren't too far behind with 192 -- good for third in the league, behind the Blue Jays (194).
Josh Reddick's RBI triple tied the game in the bottom of the second, and Josh Donaldson's fifth-inning two-run homer would give the A's a lead they would never relinquish. Donaldson's blast to left field off lefty John Danks was his team-leading eighth of the season.
Oakland added on in the seventh courtesy a two-run double off the bat of Jed Lowrie, which doubled as the shortstop's 500th career hit.
For Johnson, who appeared close to regaining the closer's role, it was just the second earned run allowed in his last 13 innings. But it's his seventh allowed in 10 appearances at home, where opponents are hitting .444 against him. On the road, they're batting just .194.
Johnson again heard boos from the home crowd upon his exit.
"The way the inning started, if Chavy gave up a hit, it was going to be Abad for the next guy," said Melvin. "Johnson for the righties, and if we needed a backstop, then we had Doolittle. I didn't want to get to that point, but that's how it happened.
"I'd like to say a win's a win. Doolittle pitched great."
"At the end of the day," said Chavez, "they got the job done."