The 22-year-old slugger, who is no stranger to adversity, made up for it at the end.
Singleton shook off a game that included two strikeouts and a pair of errors at first base to homer in the eighth inning for his first major league hit and help the Houston Astros to a 7-2 win over the Los Angeles Angels.
Singleton was surprised by how he felt after he launched a towering shot off Matt Shoemaker into the bullpen in right-center to make it 6-2.
"I was taken back. It felt like I'd never done it before, to be honest," said Singleton, who slugged 75 homers in the minors. "It felt like it was something new. My heart was racing so fast once I hit home plate, it didn't make any sense. I was still excited, still pumped from the adrenaline."
Singleton, a highly touted prospect expected to help Houston back to respectability, made his major league debut a day after agreeing to a five-year, $10 million contract. Fellow young talent George Springer, who was called up in April, stood up in the dugout cheering and yelling as Singleton rounded the bases on his homer.
The players danced and laughed together when Singleton returned to the dugout, a rare scene in recent years as the Astros plummeted to Major League Baseball's basement.
"Winning breeds that," manager Bo Porter said of the moment. "When you start to win and your confidence continues to grow, you're going to have more fun."
Singleton served a 50-game suspension last season for a second violation of a drug of abuse. He told The Associated Press in spring training that he has an addiction to marijuana and had spent a month in a rehabilitation center last year. He moved past his problems this season and got the call to the majors after hitting .267 with 14 homers and 43 RBIs for Triple-A Oklahoma City.
He said Tuesday meant even more because of his past struggles.
"It's been a long road for the last 16 months so I can't be more appreciative and thankful of this moment I have right now," he said.
Singleton is the first Astros player to hit a home run in his first major league game since Mark Saccomanno in 2008 and the fourth overall. Saccomanno's career lasted 10 games, and the homer was the only one of his career.
Singleton joins Ken Caminiti as the only players in team history to walk and homer in their debuts.
Chris Carter followed Singleton's home run with his opposite-field shot to the seats in right field to give Houston back-to-back homers for the first time this season.
Jason Castro and Robbie Grossman drove in two runs apiece as Houston took the lead with a five-run third inning.
The Angels were done in by C.J. Wilson's lack of control. Wilson (6-5) walked a season-high five batters, including four in the third, in just 2 2/3 innings.
Wilson has been slowed by flu-like symptoms this week but was making no excuses.
"You're not going to feel 100 percent, so you just go out there and give everything you have," Wilson said.
Josh Hamilton had a solo homer in the eighth inning in his return from the disabled list after breaking his left thumb April 8. Fellow Angels outfielder Mike Trout was back after missing two games with a stiff back but left in the second inning with more back trouble.
"I just didn't feel comfortable," he said. "I didn't want to risk it by pushing it too much. ... I don't think it's that severe, but we'll see."
Collin Cowgill replaced Trout and homered in the eighth.
Wilson walked three of the first four batters in the third inning to load the bases. Castro's single to right field put Houston up 2-0. Matt Dominguez singled to load the bases again, and Wilson walked Singleton on four pitches to give the rookie his first career RBI.
Wilson struck out Carter for the second out before Grossman's full-count single drove in two more to stretch the lead to 5-0 and chase Wilson.
Houston starter Collin McHugh (4-3) allowed two hits over five scoreless innings to lower his ERA to 2.52.
All three of Hamilton's home runs this season have been in Houston. ... The Angels optioned right-hander Jarrett Grube to Salt Lake on Sunday to make room on the roster for Hamilton. ... They also selected the contract of right-hander Cam Bedrosian from Double-A Arkansas and optioned right-hander Michael Kohn to Salt Lake. Bedrosian, a 22-year-old reliever, has a 1.47 ERA in 17 games this season for Arkansas. He struck out one in a scoreless sixth. ... Houston optioned 1B Marc Krauss to Oklahoma City to make room on the roster for Singleton.
Information from The Associated Press and ESPN Stats & Information was used in this report.
Singleton Homers In Debut
Making his MLB debut, Jon Singleton hit a solo home run in the Astros' 7-2 win over the Angels.