Saturday's home match against Manchester United, a 1-0 defeat that proved to be O'Neill's last in charge, marked the start of a collaboration with the foundation of Nelson Mandela.
The Eagles were on the verge of an unlikely fifth-round victory when Petrov plunged to meet Stewart Downing's corner with a diving header to hand Martin O'Neill's side an 87th-minute equaliser.
But Brady's late point ensured a share of the spoils as Fermanagh earned a draw in John O'Neill's first competitive game since taking the Erne County job.