Facing A's right-hander Jarrod Parker, a well-rested Avila -- whose innings behind the plate dropped by more than 200 this year -- hit an opposite-field solo shot in the bottom of the fifth inning.
Avila hadn't homered in 55 previous at-bats against Oakland. He said he was looking for something high in the strike zone, and he got it from Parker with a 91-mph fastball on the first pitch.
He also said it resulted from him being able to transfer the power in his legs, unlike last year.
"It's hard to hit with no legs," he said. "Being able to drive it off my back leg like that, that means normally I'm feeling pretty good there. When I'm driving the ball like that, especially opposite field, it's a good sign."
Avila had a few theories why he felt healthier heading into the playoffs this time around.
For one, the addition of Gerald Laird was huge. After watching Avila go from the starting catcher for the 2011 All-Star Game to deteriorating in October, manager Jim Leyland and president/general manager Dave Dombrowski sought out to sign a formidable backup. Laird, who played for Detroit from 2009-10, fit right in with the pitching staff and has eaten up 400-plus innings.
And second, following an MRI on his knee earlier in the season in Texas, it not only eased Avila's mind knowing there was no career-threatening structural damage, but he said the new treatment that followed worked miracles.
"When I had the MRI in Texas and we were able to put something together to minimize the pain, stuff like that, that's definitely worked," Avila said.
One game's a small sample size, especially since the 25-year-old is considered to have had a down year -- batting .253 with nine homers and 48 RBIs. He's also missed time with several injuries, including the knee pain, a right hamstring strain and a concussion.
But the injuries and missed time, he believes, might have actually played into his favor.
"Maybe it's a blessing in disguise now because I feel pretty good," he said. "I definitely would've liked to play more games during the season, but obviously with all the injuries that I had, I couldn't. And now I feel read good physically. Hopefully I can ride that a little bit."
Despite the big night, Leyland said he doesn't plan on making a change for Game 2 on Sunday at noon ET on MLB Network. Laird will platoon against the left-hander, Tommy Milone, as he's done all season.
The performance by Avila was still a welcome sight.
"That was great," center fielder Austin Jackson said. "It helps his confidence going into this series, and at the same time it really doesn't matter what you do during the season. It's a good sign for him to come out and swing it well."