Oakland will shut down Davis from swinging for five days before they revisit the injury.
Davis was lifted from Tuesday's game against the Cleveland Indians due to the ongoing issue with his left side.
The slugger was expected to be placed on the IL earlier this week but Oakland opted to wait to see whether his condition improved after a few days off.
Davis suffered the injury May 5 on the road against the Pittsburgh Pirates during one of his rare appearances in the outfield. He crashed into a railing in foul territory while chasing down a fly ball in left field.
The 31-year-old is hitting .248/.318/.497 with 12 home runs and 29 RBIs in 43 games.
Davis leads MLB with 145 home runs since the beginning of the 2016 season, which is 18 more than second-place Nolan Arenado.
In a corresponding move, outfielder Skye Bolt was recalled from Triple-A Las Vegas.
The 25-year-old has three games of big-league experience under his belt. He recorded his first hit in the majors - a double - against the Pirates on May 4.