He's one of the players expected to help the Houston Astros back to respectability after three straight 100-loss seasons.
All that despite a couple of significant setbacks. And for the first time publicly, he's opening up about his battle with an addiction to marijuana and monthlong stay at a rehabilitation center.
"At this point it's pretty evident to me that I'm a drug addict," he told The Associated Press over breakfast on a recent day near the Astros' camp. "I don't openly tell everyone that, but it's pretty apparent to myself."
"I know that I enjoy smoking weed, I enjoy being high and I can't block that out of my mind that I enjoy that," he said. "So I have to work against that."
Hours after the AP story moved, the Astros released a statement and commended Singleton.
"We applaud Jon for the courage he has shown in tackling this issue head on. He has displayed a great deal of maturity and commitment over the past year and has the full support of the Astros organization," the team said. "He is on the right track for his baseball career, and, more importantly, for his life. We are very proud of Jon."
Singleton had steadfastly avoided discussing the subject for more than a year.
The 6-foot-2, 235-pound Singleton—he's listed as Jonathan, but says he prefers Jon—sits up straight in a small booth, adjusts the baseball cap he's wearing backward and fills in the details of his private struggle.
The 22-year-old says he has stopped using marijuana and is better now. He's determined to rebound from a season that was all but lost because of his addiction and make his major league debut.
General manager Jeff Luhnow said Singleton could start the season with the Astros, but it's too early to know for sure. Singleton has been playing in the big league spring training games, and went 0 for 2 Monday in a 4-0 win over Miami.
"He's still young and still learning both about baseball and about life," Luhnow said.
It's no secret that Singleton, acquired by Houston from the Phillies in the 2011 trade for Hunter Pence, has had issues with marijuana. He was suspended for the first 50 games of last season for a second failed drug test. Back then, it was simply characterized as a mistake, or "a lapse in judgment" as his statement said.
That certainly wasn't the real story.
His first positive test came in June 2012 and he said he quit using marijuana for the rest of the season. He went on to hit .284 with 21 homers and 79 RBIs in his first season in Double-A.
At season's end, he went to the Arizona Fall League and quickly fell back into old habits.
He knew his situation was dire when he failed a second test in December 2012, but he continued to get high every single day.
The 50-game suspension came a month later and he was summoned to Houston to meet with manager Bo Porter and to see a therapist, who evaluated him for addiction. It was evident to him that he needed help.
Singleton was immediately admitted for a monthlong stay at an inpatient rehabilitation center.
"I knew I had a problem," he said. "Even after I failed the second drug test I couldn't stop smoking weed. It was really bad. Me going there was definitely the best move."
He didn't feel that way when he first entered. Fearing the unknown, he says he didn't sleep for three days straight.
"They would turn off the lights at 11:30 and I would just sit there and stare at the ceiling because I couldn't go to sleep," he said. "My heart was beating too fast. I would get night sweats. It was bad. I legitimately went through withdrawal."
Singleton desperately wanted to leave and wasn't open to the recovery process.
"But after I was there for so long it just grew on me," he said. "I was like, 'I'm going to be here for 30 days, so I might as well get the best out of it that I can.' I used it as a learning experience."
At a time when he should have been getting in shape for spring training and a chance to make Houston's major league roster, he instead spent his days attending classes and therapy sessions with other addicts in a program for young adults.
One thing he didn't do: Dwell on his missed opportunity.
"Not so much, because I knew I got myself into the situation so I had to deal with it," he said. "It wasn't like, 'I got myself here, now I hate myself.' It was like: 'I got myself here so I can't be mad at anybody but myself.'"
Though just 21 when he entered rehab, he'd already had a long history with marijuana, using the drug "on and off" since 14. He blamed his start on the culture growing up in Long Beach, Calif., where he estimated 80 percent of his friends not only knew where to get marijuana, but also how to get it within an hour.
Singleton clearly describes his first experience with the drug and how it made him feel. To put it simply, he fell in love with that feeling.
And that's what drove his addiction.
"I guess I just don't like being sober," he said. "I like to change the way I feel."
In rehab he had to identify why he needed it and how to alter his behavior to avoid its traps.
"I've got to the point now where I know what I am," he said.
His stint in rehab allowed him to quit using marijuana and he said he hasn't smoked since—a span of more than a year—even though he was moved to Houston's 40-man roster in October and can no longer be tested for the drug.
Last season when he made his debut in Triple-A after stopovers in both Low-A and Double-A following his suspension, he struggled. He hit just .220 in 73 games and his old demons resurfaced.
"I went through some slight anxiety, some depression because I wasn't being successful," he said. "That was definitely difficult and that drove me to drink."
He admits to abusing alcohol as a substitute for marijuana, getting drunk almost every day and "waking up hung over every morning."
After the season he regrouped and prepared for the Puerto Rican winter league.
"I made up my mind to be my best, so hopefully better things happen because I'm not going out drinking and partying and doing all that kind of crazy stuff," he said.
His changes paid immediate dividends. He hit a league-leading nine homers in Puerto Rico and batted .268.
Singleton reported to camp in good shape and in a better place mentally than last spring, hoping to show Luhnow he's ready to compete for Houston's first base job.
The team has been supportive during his battle, but Singleton knows he'll have to stay clean to reach his goals.
He isn't receiving any treatment for his addiction, isn't currently in a program and doesn't have someone traveling with him to keep him on track.
Singleton is confident he can avoid a relapse by focusing on his opportunity, keeping better company and avoiding bad situations. He calls his life a work in progress and is focused on not being so hard on himself this season.
"Recently I've been more or less just sticking to myself and worrying about what I need to do to get better and become better as a person, not just a baseball player," he said.
If he's able to do that, the Astros foresee a big future.
"My expectation is that with everything that happened to him, we want to build up the positives from the end of last year," Luhnow said. "And get off to a real good start in Triple-A and then force his way onto the roster in Houston."