Teenager James Perch also tested Sullivan, but Wales striker Gareth Taylor struck the angle of post and bar with a header just after the break.
Substitute Commons missed from the spot after Gary Kelly brought him down - but in the dying minutes, Perch was carried off after colliding with Sullivan.
Leeds boss Kevin Blackwell:
"It was disappointing not to win the match but we have only suffered three defeats in 17 games.
"And we are still in contention for the play-offs - at the beginning of the season people were tipping us to be in Forest's position.
"I don't think our goalkeeper had that much to do. And we were the away side."
Nottm Forest: Gerrard, Louis-Jean, Morgan, Thompson, Doig, Curtis (Robertson 29), Perch (Harris 90), Gardner, Bopp (Commons 57), Taylor, James.
Subs Not Used: Doyle, Beaumont.
Booked: Thompson, Doig.
Leeds: Sullivan, Kelly, Butler, Kilgallon, Pugh, Lennon, Walton, Wright (Johnson 66), Richardson (Carlisle 7), Hulse, Healy (Deane 78).
Subs Not Used: Pressman, Einarsson.
Booked: Healy, Kelly, Hulse.
Ref: G Salisbury (Lancashire).