MLB legend Gary Sheffield is going to bat for Tim Tebow ... saying he's worked with the aspiring baseball player and the dude is a NATURAL!
"I spent time w @TimTebow in the cages recently," Sheffield tweeted.
"He's a NATURAL. I absolutley believe in his ability to play in the bigs. Tim has IT #focused."
Sheffield was a 9-time MLB All-Star and the NL batting champion in 1992.