Hearts stumbled in their pursuit of a first league title in 66 years as a 1-1 draw at Motherwell kept Celtic and Rangers in the hunt before the Old Firm face off on Sunday.
Aiming to become the first side apart from the Glasgow giants to win the Scottish league since Alex Ferguson's Aberdeen in 1984/85, Hearts stretched their lead at the top to four points.
But Celtic can cut the gap to one with victory at home to Rangers and now know winning their final three games will see them retain the title with Hearts still to go to Celtic Park on the final day.
Dropped points for Hearts means Rangers are not mathematically out of the title race either as they are eight points off the top with three games to play.
Hearts boss Derek McInnes was left fuming his side were not awarded a late penalty as referee Steven McLean stood by his original call despite being asked by VAR to review a potential foul by Tawanda Maswanhise on Alexandros Kyzirids.
For the fifth game in a row, McInnes' men had to came back from a goal down.
Stephen Kingsley turned into his own net under pressure from Ibrahim Said on 25 minutes.
Lawrence Shankland should have given Hearts the perfect start when his shot was blocked by Stephen O'Donnell with the goal gaping.
The Scotland international made amends just before halftime with a smart finish after Calum Ward could only parry Michael Steinwender's strike.
O'Donnell thought he had restored Motherwell's lead early in the second half, but the goal was ruled out for offside.
Then came the controversial moment at the other end when Hearts were not awarded the spot-kick after Maswanhise stepped on Kyzirids from a corner.
McInnes was booked in the aftermath of the referee taking the unusual stance of sticking by his original call.
Hearts piled forward but could not find the winner that could have set up the chance to clinch the title at home to Falkirk on Wednesday.