A league source told ESPN NFL Insider Adam Schefter of Leinart's release earlier Monday, which the former Heisman Trophy winner confirmed on Twitter.
"I appreciate and thank (Texans owner) Mr (Bob) McNair and the Texans organization for giving me the opportunity to play. I will miss the Texans fans and most Importantly my teammates. I have no time to get down, focus is on getting healthy and being ready to go again! #believe," Leinart wrote.
The left-handed Leinart finally got the chance to start for Houston after Matt Schaub broke a bone in his right foot on Nov. 13, but Leinart fractured his left collarbone in the second quarter of his first start since 2009.
Rookie T.J. Yates, a fifth-round draft pick out of North Carolina, took over after Leinart's injury and led the Texans to the franchise's first AFC South title and first playoff victory.
Winston, a former third-round pick by Houston, also tweeted his release.
"Unfortunately I have bad news. The Texans have decided to release me today. Although it is a surprise, I have nothing but positive memories," Winston wrote Monday, "And great relationships that I have built over the years. While my future seems uncertain, I am confident I will land on my feet."
Winston thanked Houston's fans, the Texans organization and McNair in subsequent tweets. His release saved the Texans $4.5 million.
Winston has started 87 of 92 games for Houston since being the 66th overall pick out of the University of Miami in 2006.
Houston signed Leinart as a free agent just before the 2010 season, ending the former Southern Cal star's stormy tenure in Arizona. Leinart was drafted 10th overall by the Cardinals in 2006, and played in 12 games as a rookie under coach Dennis Green.
When Leinart broke his collarbone in 2007, Kurt Warner took over and Leinart mostly watched from the sideline over the next 2½ seasons. Warner retired after the 2009 season, but Leinart clashed with Arizona coach Ken Whisenhunt and he was released in September 2010.
He didn't take a snap in 2010 but felt comfortable enough with Texans coach Gary Kubiak and the offense that he decided to rejoin to Houston as a backup instead of competing for a starting job elsewhere.
Information from ESPN.com senior NFL writer John Clayton contributed to this report.