The highly regarded prospect will have surgery, with the team hoping he will be ready to return in time for spring training next year.
It has been a frustrating year for Sanchez, 22, after an impressive debut season in 2020 for Miami. He went 3-2 in seven starts last year as the Marlins advanced to the playoffs, sporting a 3.46 ERA with 33 strikeouts in 39 innings. He also made two postseason appearances.
But his return to the club for spring training fell off track, as the Dominican right-hander was delayed by a visa issue and then a false positive on a COVID-19 test.
“I don’t feel frustrated, but it was a weird feeling,” Sanchez said at the time, via a translator. “That false positive spoiled my momentum, but I’m not that far behind. I just can’t pitch as many innings as the other guys.”
He did not appear for Miami in the regular season.
“We know what we have with Sixto,” manager Don Mattingly said during spring training, resigned to letting the prospect regain his momentum on his own schedule. “It’s just a matter of getting the process started for him.”
The Associated Press contributed to this report.