Sheffield United were beaten late on by Swindon Town, while perennial play-off failures Preston North End secured a first-leg advantage.
Swindon Town left it late to seal the first-leg advantage in their League One play-off semi-final first leg at Sheffield United, while Preston North End were 1-0 winners at Chesterfield.
Nathan Byrne's strike from the edge of the box deep into stoppage time saw Swindon fight back from a goal down to prevail 2-1.
Kieron Freeman had put the hosts ahead at Bramall Lane before Swindon's Ben Gladwin saw his penalty saved by Mark Howard.
But Samuel Ricketts' powerful header drew the visitors level before Byrne's late heroics.
Preston, seeking a first promotion via the play-offs at the 10th attempt, finished 20 points ahead of Chesterfield and underlined their superiority with a goal after six minutes.
Jermaine Beckford coolly chipped the ball over the onrushing Tommy Lee and Preston will take a slender lead back to Deepdale on Sunday.