KANSAS CITY, MO. – Aaron Thompson, the 28-year-old rookie, is learning how gut-wrenching losses on the major league level can be.

He didn't do his job on Wednesday, walking Eric Hosmer, a lefthanded hitter that the lefthanded Thompson is supposed to get out. It ended up one of the checkpoints along the way to the Twins blowing a lead and losing 6-5 to the Royals. The team took the loss hard, but it was a swing game that often shows what a team is made of.

"When you lose on this level, it stinks," Thompson said. "It's not, 'Oh, we have another game tomorrow.' "

Then he added: "Games like that, a one-run game, it was cool to be part of that fight."

It's an acquired perception for Thompson, a first-round draft pick (22nd overall) by the Miami Marlins out of high school in 2005.

He has already learned how gut-wrenching it can be to put a career in jeopardy.

Thompson tested positive for marijuana in 2012, his second suspension in three years for drug abuse. The penalty at that time was a 50-game suspension — and it came just a few months after signing with the Twins as a minor league free agent.

"It was a major derailment in terms of my personal life," Thompson said. "I'm a Christian, and I can talk for days about what a blessing that was and the things I got to do at home. That really refueled me for this second leg of my career.

"I had a little brother who was a freshman in high school. I never saw him play baseball, because I'm always playing baseball," he said. "I was able to go work with him and the team and I felt like a brother, not a baseball player. I went to a men's conference with my brother and stepdad. I was making lemonade out of lemons. It stunk, but there was something to learn here."

The Twins weren't happy, but General Manager Terry Ryan stuck by Thompson.

"He has worked hard to get where he is at today," Ryan said. "The suspension happened a long time ago and has been put in the past by the team and the player as a lesson learned."

Thompson split 2013 between Class AA New Britain and Class AAA Rochester. In 2014, he went 3-3 with a 3.98 ERA at Rochester and earned a September call-up. It was his first time in the majors since 2011, when he made one appearance in August and three in September with the Pittsburgh Pirates.

He has made it back, and it just so happens to be because of a drug suspension. Ervin Santana tested positive for the banned substance Stanozolol just before the Twins broke camp and is serving an 80-game suspension. Mike Pelfrey was elevated from the bullpen to take Santana's spot in the rotation. Thompson was called up from Class AAA Rochester, and was on an Opening Day roster for the first time in his career.

So this is his shot.

"I didn't learn a lot about baseball during my suspension," he said, "but I learned a lot about myself. You have to accept it and use it as something to build upon instead of hide from."

Scouts believe he has the breaking ball to get lefties out on the major league level, but Thompson — whose fastball reaches the low 90s and who also throws a changeup — is out to prove he can handle any situation.

Twins manager Paul Molitor has used Thompson to match up against lefthanded hitters, and Thompson also has pitched two innings in a game three times. He has a 0.82 ERA through 11 innings with three walks and five strikeouts.

"He's been a big plus for us, coming up the way he did, getting the late call," Molitor said. "He's versatile. I feel really good if it's a left-on-left matchup but he's also a guy I can extend."

The second positive drug test, and resulting suspension, could have been the end for Thompson. Call him a late bloomer, but he's figured out enough things to get another chance at a major league career.

"It's fun to look back and go, 'Hey, I could have quit there,' " Thompson said, "but the Twins gave me an opportunity.''