The Orioles on Monday reinstated outfielder Austin Hays (fractured rib) from the injured list and placed first baseman Chris Davis on the IL because of patellar tendinitis in his left knee.

Hays, who started in left field against the Braves on Monday night, batting ninth, hasn’t seen any action since the middle of August. He was hit by a pitch on Aug. 6 against the Marlins, and he ran into the center-field wall at Citizens Bank Park a week later.

Hays went 2-for-4 in his return, scoring twice in Baltimore's 14-1 victory.

After resting for a few weeks, Hays went to the Orioles' alternate training site in Bowie, Md., and was able to take ample at-bats.

“[Hays] received 25 to 20 at-bats in the last week,” manager Brandon Hyde said prior to the series opener vs. Atlanta. “I talked to him in my office a half-hour ago, and he feels really healthy, and he said his legs feel great. He was appreciative of all the at-bats he received, and now he is ready to go.”

Davis has been in and out of the Orioles' lineup because of his knee problems. The last time he played was on Friday against the Yankees; he went 0-for-3.

Davis was supposed to add power, but he is having one of the worst seasons of his career, going 6-for-52 with one RBI. It’s not known if he is out for the season.

With Hays back in the lineup, Ryan Mountcastle was moved to the DH spot, and he made the most of it, going 3-for-5 with three RBIs.

Mountcastle will also see time at first base now that Davis is on the IL.

“[Mountcastle] has played infield his whole life,” Hyde said. “He has been doing some work at first base [on the Major League side], in the [alternate training site], and he played some in Spring Training. So it’s not like he is unfamiliar with the position. We feel he can make the transition there.”

Worth noting

Outfielder Mason Williams has cleared waivers and been assigned to the alternate training site, while infielder/outfielder Stevie Wilkerson has been released.