Adrian Peterson -- I'm Fast, Lean & Ready for NFL Return

Adrian Peterson is erasing all thoughts of retiring from the NFL -- and is ready and able to get back on the field ... TMZ Sports has learned.

Peterson was in federal court Friday ... appealing his suspension in an effort to get reinstated immediately -- and sources close to AP tell us he'd be ready to practice tomorrow, if he got the call.

We're told Adrian has been working out twice a day since the NFL blocked him from playing in November -- and his renowned physique is intact -- still less than 4% body fat, is what we're told. He's even put a gym in his Texas home.

The court hearing in Minneapolis ended without a decision, and both sides will be back in court Monday.

Back in December, Adrian said he was considering quitting football altogether -- but we're told he's game-ready and taking the same approach he took after tearing his ACL in 2011.

The former league MVP flashed his wheels last weekend in a street race with Kevin Hart. Not exactly pro-level comp, but AP did spot him 5 yards.