The NFL's MVP through the first 3 weeks ain't cashing in on his early season success ... 'cause Patrick Mahomes' agent tells TMZ Sports -- NO BIG DEALS UNTIL THE OFFSEASON!!
Leigh Steinberg -- the super agent who represents the Chiefs' QB -- says it's all part of a plan to make sure Patrick keeps a level head throughout his first year as a starter.
"We're being very, very careful to allow this season to proceed without his face on every billboard," Leigh tells us.
"Without it creating a situation where he throws the first interception and people are saying, 'Well, why's he on every billboard??'"
Don't get it twisted ... Mahomes -- who's tossed 13 TDs with no picks in K.C.'s 3-0 start -- has done SOME deals ... BUT, the big fish are currently on ice.
"We're keeping it low key," Leigh says. "And, once the season is successfully over, then we'll go into marketing in a lot of different brand categories."
BTW ... if you were wondering what Patrick's eyeing for his first big endorsement -- Steinberg tells us Mahomes' mug could be on a cereal box near you this winter.