Clemens earned about $160 million and won 354 games in a 24-year career with the Red Sox, Blue Jays, Yankees and Astros. His 4,672 strikeouts are third-most and he was picked for 11 All-Star games.
Clemens bounded into the home clubhouse a little more than an hour and a half before the game wearing a gray Longhorn shirt, jeans and cowboy boots and bellowed, "how we doing, how we doing?" as he walked through shaking hands with his teammates.
His highlighted blond hair was a bit spiky on top, causing a couple of his teammates to ask each other if he'd gotten a new haircut.
One fan held a sign which read: 'The Rocket has landed in Sugar Land,' and children squealed with delight as he came on the field to warm up about 30 minutes before the game.
Clemens has spent much of his time out of baseball defending his reputation.
He was accused by former personal trainer Brian McNamee in the Mitchell Report on drugs in baseball of using steroids and HGH, allegations Clemens denied before Congress. The Justice Department began an investigation into whether he had lied under oath, and in 2010 a grand jury indicted him on two counts of perjury, three counts of making false statements and one count of obstructing Congress.
He was acquitted of all the charges on June 19 after a 10-week trial and had largely stayed out of the public spotlight until now.
Many of his former teammates have said they believe that he could pitch again in the majors.
Clemens had two great seasons with the Astros after he turned 40, going 18-4 with a 2.98 ERA in 2004 to win his record seventh Cy Young Award. He was 13-8 with a career-low 1.87 ERA in 2005 while helping his hometown Astros reach their only World Series, and the team has already said it wouldn't rule out bringing him back this year.