Derek Jeter -- Real Talk from Obama ... 'For a Baseball Player, You Were Old!' (VIDEO)

Derek Jeter tried to convince President Obama he's still a pretty young guy ... despite what the sports media may think.

Obama responded by KEEPIN' IT REAL, SON!

It's a pretty great clip ... Obama sat down with the Yankees legend for an interview with "The Players' Tribune" -- and was trying to get some retirement advice from Jeter.

That's when Jeter complained that sports media labels people as "old" when they hit age 30.