Hall of Fame pitcher Pedro Martinez, who won a World Series with Ortiz in 2004, shared a picture of him hugging his former teammate.
"I'm at peace knowing you out of danger," Martinez wrote on Twitter. "You a strong man Compai, can't wait to hear your voice."
Former Chicago White Sox designated hitter Frank Thomas also tweeted his prayers to Ortiz. The two work together for Fox Sports' baseball coverage.
"So happy to hear the encouraging news of a full recovery," Thomas wrote.
Former Red Sox first baseman Kevin Millar posted a lengthy message on Instagram. Millar praised Ortiz's dedication and love for his fans.
"Papi the Millar family prays for strength and courage during this brutal attempt to cause harm to such a great man!" Millar wrote. "A man that has never said no to an autograph or high five from a little boy or girl.... sorry for this buddy."
Longtime MLB pitcher Tim Wakefield was teammates with Ortiz from 2003 to 2011. Wakefield asked his followers to keep Ortiz in their prayers "while he recovers from this senseless act of violence."
"Be strong big fella, we got you," Wakefield wrote.
"No coward can take down a super hero like you," Youkilis wrote.
Arizona Diamondbacks outfielder Adam Jones and Ortiz were AL East Division rivals when Jones played in Baltimore from 2008 to 2018. Jones shared a photo of him and Ortiz pointing to the sky on Instagram.
"You have the support of sooo many that love, adore, and respect the hell outta Papi," Jones wrote.