Hogan and Flair had some of the greatest matches in wrestling history -- battling dozens of times over the years ... starting in the early '90s.

After Flair underwent surgery on Monday, Hogan issued a statement saying, "Ric Flair only prayers, love and positive thoughts."

"Now it's time to kick out because you can and you will always be 'The Man' my brother."

Flair is recovering from surgery, his family is by his side. Ric's reps say the procedure went well -- but they wouldn't say what the procedure was.