(SportsNetwork.com) - The Baltimore Orioles will welcome slugger Chris Davis back into the lineup on Tuesday when they continue a season-opening three-game series with the Tampa Bay Rays at Tropicana Field.

Davis was suspended for 25 games last season for using amphetamines without a prescription. He served 24 games last season and was suspended for the first game this season.

The 29-year-old Davis said he was diagnosed with ADHD in 2008 and that he took Adderall to help him better function in everyday life. He had been granted a therapeutic-use exemption for the drug by Major League Baseball in previous seasons but was denied in 2013, when he led the majors with 53 homers and 138 RBI.

He did not reapply for an exemption last season, when he admitted to taking Adderall multiple times to help his focus. Of course, he slumped badly in 2014, as he saw his average drop nearly 100 points to .196 and his production cut nearly in half before he was suspended for most of the final month of the season after a second positive test.

Davis has since been granted an exemption for a similar prescription drug, Vyvanse.

"I think just mentally, I didn't really know where to go," Davis told the team's website. "I've never really been in that situation before, but this year, I'm a lot more relaxed and I almost kind of have that chip back on my shoulder."

Wei-Yin Chen will be on the hill for the Orioles on Tuesday, as he tries to follow up his best year in the majors.

Chen enjoyed a career season a year ago for the Orioles, going 16-6 with a 3.54 ERA. He was sharp this spring too, as he pitched to a 2.45 ERA over 18 1/3 innings.

The Taiwanese lefty has faced the Rays 13 times and is 3-4 against them with a 3.26 ERA.

Tampa, meanwhile, will hand the ball to 27-year-old righty Nathan Karns, who is on an Opening Day roster for the first time in his career and will be making just his sixth big league start.

Karns has gone 1-2 in his brief major league career and has pitched to a 6.00 ERA. The home run ball has been his Achilles' heel, as he has surrendered eight in 24 big league innings.

He earned a spot on the Rays thanks to injuries to Alex Cobb, Drew Smyly and Alex Colome. Karns was 2-2 this spring with a 3.86 ERA. However, six of the nine earned runs he allowed came in one outing.

Baltimore improved to 5-0 on Opening Day under manager Buck Showalter on Monday, as Chris Tillman delivered 6 2/3 innings of one-run ball in the Orioles' 6-2 triumph.

"This guy is a perfectionist he will critique himself. He'll probably talk about some walks ... but he's got great presence," Showalter said of Tillman. "You know he's capable of handling that situation. Proud of him."

Alejandro De Aza, Steve Pearce and Ryan Flaherty all homered for the Orioles, while De Aza and Travis Snider each drove in two runs in the win.

"Those guys you can tell they prosper in the environment they are in and let's keep creating it," Showalter said. "It's fun to watch. They care about playing the game right."

Chris Archer (0-1) allowed four runs -- three earned -- with five strikeouts in 5 2/3 innings for Tampa Bay.

Baltimore won 12 of its 19 matchups with the Rays last season.