To enable these codes you must win the simulations. Once you've done that, turn on the Genesis and enter the desired code after the Sega screen appears but before the Acclaim screen appears.

Effect Code

NFC/AFC mode A, B, A, B, A, B
Fumble mode C, A, B, C, A, B
No fumble mode B, A, B, A, B, A
No play end mode B, A, Start (x4)
Up and over dives C, A, Start (x2), A, B
Speed burst mode B, A, C, C, A, Start
Rookie team mode Start, A, Down, A, Start, Start
Super slippery mode A, A, A, A, A, A
Iguana/Acclaim mode Down, A, Down (x2), A, Down
Blackout mode Start, A, Down, Start, A, Down
Grenade mode Down, Down, Start, Down, Down, Start
Stealth mode Start (x2), B, Start (x2), B
Power team mode B, A, Down, A, Start, Start
Chaos Ball Mode Down, Start, C, A, B, Down