Singleton told The Associated Press he was heading to Baltimore on Monday to join the team for the opener of a three-game series with the Baltimore Orioles, who have the best record in the American League.
The first baseman adds depth at a position where José Abreu is the starter. Abreu has underperformed in the first year of a three-year, $58.5 million contract, hitting just .237 with 10 homers and 56 RBIs.
The left-handed slugger has been playing at Triple-A Sugar Land after signing a minor league deal with the Astros on June 24 following his release from the Brewers. Since joining the Space Cowboys, he has hit .333 with 12 homers, 28 RBIs and a 1.138 OPS.
Singleton was in the Astros organization until before the 2018 season, when he asked for his release after being suspended 100 games after a third positive drug test while playing at Double-A Corpus Christi. He was regarded as one of the top infield prospects while with the Astros organization from 2011 until his release after being acquired in a trade with Philadelphia.
Singleton didn't play organized baseball from 2017 until 2021, when he restarted his career in the Mexican League. After his release from the Astros, he didn't plan on playing baseball again.
He discussed that time period this past weekend in Sugar Land before he learned he'd be rejoining the Astros.
"When I did walk away from baseball, I honestly wasn't thinking about playing baseball anymore at all," he told the AP. "It wasn't even a thought. But once I started working out and going to the gym every day and things start to progress, then baseball became a thought again. So things have really come full circle."
He credited his recent success to his preparation off the field.
"I think my mindset, mentally, my mental state, that's been huge for me," he said. "The last five to six weeks, just small things I'm doing to prepare myself and just reminding myself what I need to do every day just to be ready."
The 31-year-old appeared in 114 games for the Astros in the 2014 and 2015 seasons after signing a five-year, $10 million contract. He last appeared in a major league game for the Astros on Oct. 2, 2015.
He returned to the majors for the first time since that game when he appeared in 11 games with the Brewers before his release.
Outfielder Corey Julks was optioned to Sugar Land on Sunday to make room for Singleton on the roster. The Astros were off Monday and visited the White House where they were honored by President Joe Biden for winning the World Series.