Jan Vennegoor of Hesselink headed a stoppage time winner for Celtic in a 2-1 win over Rangers, who had Carlos Cuellar sent off during the pulsating Scottish Premier League derby on Wednesday.
The victory cut Rangers' league lead to one point after a fierce contest that finished with several players trading blows at the final whistle.
Rangers manager Walter Smith declined to discuss the melee at the end of the match that continued into the tunnel but told BBC radio: "After holding out for so long (with 10 men) it was obviously disappointing to lose a goal in the last seconds."
Japanese midfielder Shunsuke Nakamura gave Celtic the lead with a 30-metre rising shot after 20 minutes.
He gathered a pass inside from Gary Caldwell and lashed a fierce shot that swerved away from keeper Allan McGregor at full stretch and into the top left of the net.
McGregor denied Celtic a second 10 minutes from the interval when Australian striker Scott McDonald ended a pounding run down the right with a 25-metre strike from a tight angle which the keeper did well to parry at his near post.
Rangers had struggled to make any impact in a tense first half but they surged back following the break and levelled through substitute Nacho Novo after 10 minutes.
The Spanish striker cracked an angled shot from 10 metres across keeper Artur Boruc into the far corner of the net.
Rangers were reduced to 10 men when Spanish defender Cuellar used his hand to divert Nakamura's net-bound shot on to the bar in the 70th minute.
McGregor saved McDonald's penalty, turning the ball against the post before gathering it in.
McGregor hobbled off with 12 minutes remaining with an ankle injury and was replaced by sub keeper Neil Alexander.
Four minutes into stoppage time Alexander was beaten by a diving header from Dutchman Vennegoor of Hesselink which flew into the middle of the net following McDonald's head flick across goal.
Rangers have 75 points from 31 games while Celtic have 74 from 33.
