"He's done a great job. He really has," manager Bob Geren said of Powell. "He's in a situation where he's behind an exceptional first catcher. He's done a super job catching.
"Obviously, getting four runs with one swing is something we haven't had a whole lot of. It was a welcome change."
Powell has driven in nine runs in his past six games. He's hit seven doubles, five home runs and has 27 RBIs in only 36 games this season. The 6-foot-3, 260-pounder is slugging .455.
"It's not frustrating," Powell said of his lack of playing time. "You always want to play more, but I know I'm a young guy. I'm just glad I could contribute today."
"Being a backup catcher is a difficult job," Geren said. "Coming in and being sharp both offensively and defensively, that's very hard to do. You don't see that too often."
The A's jumped out to a 3-0 lead in the first. Adam Kennedy walked, then Rajai Davis doubled to get things under way. Ryan Sweeney brought both of them home with a soft liner to center. Mark Ellis later scored Sweeney on a sacrifice fly to left.
Davis got the scoring started up again in the second, bringing in Eric Patterson, who had doubled and taken third on a single by Kennedy, with a sac fly to right.
After Sweeney singled and Jack Cust walked to load the bases, Powell delivered the big blow with his shot to right-center.
"With a guy on third," Powell said, "I just wanted to make sure to drive it. I got lucky and didn't miss."
Oakland got its first three runs off of Kansas City starter Brian Bannister, who left after just 1 1/3 innings with right shoulder fatigue.
The A's then tagged Yasuhiko Yabuta for five runs, chasing him after recording only two outs. They added a pair off of Bruce Chen in the third to get to 10 runs.
Trevor Cahill, meanwhile, allowed three runs in five innings, surrendering all three in the third. He gave up six hits, walked two and struck out three to improve to 8-12.
"He threw OK," Geren said. "He pitched good enough to win. You have to learn to pitch with a lead. ... It's nice to have some runs, because then you can make some mistakes."
Brad Kilby, selected from Triple-A Sacramento when rosters expanded on Tuesday, made his Major League debut in relief of Cahill. Kilby, 26, allowed only one hit in two scoreless innings. He had two strikeouts.
"He's deceptive," Geren said of Kilby. "He hides the ball very well. His velocity plays up a bit because of his sneakiness. He didn't look nervous at all.
"He really helped us. It was nice to give [Craig] Breslow, [Michael] Wuertz, [Brad] Ziegler and [Andrew] Bailey the night off and still win."
An Elk Grove native and San Jose State product, Kilby said he'd been dreaming of pitching in the big leagues for over 20 years.
"I was pretty much thinking, 'Just don't hit the first guy,'" Kilby said. "Having someone behind the dish that I've thrown to really made me feel comfortable."
"That was a cool moment," said Powell, who caught Kilby with Sacramento last season. "I looked at him and said, 'Look, the guys here aren't that different.' I just wanted to make sure he had confidence in himself."