Anthony Walker Jr. promised his pops a new ride with his first NFL paycheck -- at AGE 10.
Walker Jr. inked a rookie deal with the Indianapolis Colts 11 years later ... and boy did he come through -- hooking Walker Sr. up with a brand spankin' Lexus ES 350.
The 5th-rounder told TMZ Sports he owed it to his dad for introducing him to football ... and hearing Jr. talk about the whole thing -- including Sr.'s reaction to the car -- is pretty surreal.
FYI, the ES 350 starts around $40K -- a nice chunk of Walker's half-a-mil starting salary.
But don't worry ... the rook told us he's only making it rain this one time.