Johnny Manziel Recruited By Spring League ... Other NFL Stars Commit

Johnny Manziel has officially been invited to join an independent pro football league in April -- a league that already has commitments from ex-NFL stars like Greg Hardy and Kellen Winslow Jr.

TMZ Sports spoke with a rep for The Spring League who says Kellen and Hardy are 100% committed to play in the 4-team league which will primarily feature NFL vets and "younger talent."

The league is expecting to have reps from all 32 NFL teams at their games and believe it will serve as a showcase for guys trying to get in the league.

As for Johnny, his offer comes with 2 conditions -- nightly check-ins with a team staff member at 9:30 PM AND he must pass a USADA drug test on April 5th, the first day of the league.

We reached out to Manziel for comment. So far, no word back.

As for Kellen, he's pumped to show the world he can still compete at a world-class level.