They had the chance to tighten their grip in third and Hearts snatched it with both hands during a memorable 2-0 win over Celtic.
Jorge Grant's penalty and Lawrence Shankland's second half strike did the damage to leave the Hoops reeling. They had a chance to go top but the day in Gorgie belonged to the home side who were left jubilant at full-time. Hearts are now 15 points clear of fourth-placed St Mirren.
Referee Don Robertson and VAR had an eventful afternoon. They handed out a penalty to the Hoops for an Alex Cochrane foul on Yang, before the latter was sent off for a high boot on the Hearts defender following a VAR check.
The refereeing tech operated by John Beaton handed Grant the chance to level up the game after spotting a Tomoki Iwata handball, and only a marginal offside denied Shankland from making it two before half-time.
In the end it mattered not as he struck after the break to have the last laugh over Joe Hart, who TV footage appears to show him accusing Shankland of bottling the penalty taking, in more blunt terms.
Photos have arrived from the game and there are some crackers. The Edinburgh Evening News shows 13 of the best.
1. Ref controversy begins
Don Robertson and VAR certainly put themselves in the headlines with their first half performance. Yang went down under a Cochrane tackle and one that some think falls in the soft category. | SNS Group
2. Big stop
A big save from Zander Clark early in the game, who was an impressive performer throughout the day. | SNS Group
3. Everyone takes a peek
It wasn't just the referee who got to see replays of the Yang red card incident... | SNS Group
4. Marching orders
Safe to say some Hearts fans were delighted to see Yang sent off following a VAR check for his high boot on Cochrane | SNS Group