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?