Down to Caddie for Tiger Woods

... He's Back, Baby!

Michael Bolton is PUMPED on the Tiger Woods comeback tour -- and says he's down to hit the links with Tiger ... as his caddie!

FYI, Bolton's been tearin' it up on the celeb golf circuit for years ... and giving Woods words of encouragement whenever they cross paths.

"Every time I see him, I tell him, 'Just win.' And he says, 'I'm trying,'" Michael told TMZ Sports.

So now that Tiger's crushin' it on the green again, we had to ask if the pop rock legend had any plans to tee off with him.

Bolton seemed a little intimidated by going toe-2-toe, BUT -- "I'd carry his bag."