Cleveland Indians superstar Trevor Bauer says he received death threats after getting rocked in his start Monday night ... claiming one fan told him, "I will kill you."
Bauer -- one of the frontrunners for the AL Cy Young this season -- gave up 10 hits and 8 runs to the White Sox ... and when he returned to the locker room to check his phone, he says it was filled with hate.
"I really hope you and your family die in a car crash," Bauer says one fan wrote.
"I am Chinese. I will kill you," he says another sent him.
Bauer claims one even said, "How do u let white sox smack the sh*t out of u. F**king f**."
Bauer took to Twitter to blast Instagram for allowing the comments to hit his phone afterward, saying, "Stop online harassment, bullying, and hate speech."
"@instagram your platform doesn’t seem to give me a way to report this crap. Do you condone this type of behavior on your platform?"
Bauer's been one of the top pitchers in the MLB this year ... he was 4-1 heading into Monday's start.
We've reached out to both the pitcher and Instagram for comment ... so far, no word back.