Reddick is leading the A's with eight homers, putting him on a pace to hit around 40 for the season.
"We knew he had some power for a slight guy," Manager Bob Melvin said. "He extends and uses his lower half. The power was always there. I knew that talking to [hitting coach] Chili [Davis], who had him last year in Boston."
Reddick, the key player the A's got from the Red Sox in exchange for closer Andrew Bailey, has established himself as he A's No. 3 hitter, raising his average to .292.
"He's getting the opportunity to play every day and the confidence of us putting him in the No. 3 spot," Melvin said. "He doesn't get pinch-hit for against left-handers. I don't move him down in the lineup against left-handed starters.
"I think he's settling in to that spot and he's very comfortable."