Hearts' unbeaten Premiership start ended at Aberdeen after Celtic's stoppage-time stunner cut their lead at the top of the table.
Rangers remain on a winning run under Danny Röhl - they left it late for a controversial victory at home to Livingston - and they are behind Hibs on goal difference after another impressive showing from David Gray's side.
It is now one win in four games for the Jambos as they anxiously wait for an update on top scorer Lawrence Shankland's injury.
Title talk was high as Hearts went 12 games unbeaten, but will it be a repeat of Aberdeen last season?
Jimmy Thelin's side won 10 of their first 11 before going 14 straight matches without a win, finishing fifth in the Premiership.
There was no panic from Hearts head coach Derek McInnes after Sunday's defeat, while SportNews' Kris Boyd pointed out they "weren't bad in the game" at Pittodrie.
"We're not perfect. We knew that," McInnes told SportNews.
"Sometimes you learn about your squad and you learn about your team when you lose a game,"
"The players know what we could have done better. But I know it's there. I know the quality's there. I know the work ethics are there and the motivation's there.
"We look forward to going again next week."
Hearts face Motherwell and Kilmarnock before a trip to Celtic Park on December 7, live on Sky.
"It's one win in four for Hearts, which will be a slight concern," Boyd added.
"The two players that have had rave reviews, Alex Kyziridis and Claudio Braga, they weren't on it today. They had lovely touches, but never really created much.
"It just wasn't to be for Hearts in front of goal. I think Derek's got to take the positives from that.
"It's a defeat, it's one that will hurt them coming up here as well but there are signs that Aberdeen have been improving.
"For Hearts, you maybe start to be a little bit worried."
Celtic struggled at St Mirren as they relied on a moment of magic from captain Callum McGregor to secure a late win.
There were more chants of "sack the board" as the Hoops fans continued to voice their frustration at the club's hierarchy a day after the AGM was abandoned.
Johnny Kenny, who had scored in their last two league outings, struggled up front and was taken off at half-time, while Daizen Maeda struggled against Buddies defender Alex Gogic.
Celtic managed just two shots on target with interim manager Martin O'Neill saying a draw would have been a "fair result," but you wonder how pivotal that 95th-minute stunner from McGregor will be heading into a hectic festive period.
"I think at a difficult time for the club, you need your leaders to step forward and he did that in the right way, when it mattered. It looked like the game had gone for Celtic. Brilliant finish," former Celtic striker Chris Sutton said on SportNews.
"He's a class player, he always has been. Just imagine this Celtic team without Callum McGregor. There's been a few fans suggesting that he's had his best days.
"I still think he has such an important role for this Celtic team and leading from the front. He's such a class player. As I said, think of a Celtic team without Callum McGregor.
"I can't imagine a Celtic team functioning as well as they do, if and when he eventually goes. Right now, he's a brilliant player and he's stepping up when it matters and that's what Martin O'Neill will demand from him."
Rangers made it four Premiership wins under Danny Röhl, but it was not without controversy and their performance was unconvincing at times.
Röhl had to dig deep into his squad. He fielded an unusual centre-back pairing of Emmanuel Fernandez and Wolves' loanee Nasser Djiga, while Brazilian striker Danilo led the line.
Fernandez headed the hosts ahead with his first goal since joining from Peterborough, but he was culpable for Livingston's equaliser and was fortunate not to be punished for a handball in the box.
There was the usual unrest in the stands before Mohamed Diomande tapped into an empty net to keep the Ibrox side fourth, trailing Hibernian on goal difference.
While the focus has been on their Edinburgh rivals and the Old Firm, Hibernian have continued their impressive start to the season.
Kieron Bowie shone as they beat Dundee 2-0 at Easter Road on Saturday to remain in third place, ahead of Rangers on goal difference and five points behind Celtic, albeit both teams have a game in hand.
The 23-year-old forward was left out of Steve Clarke's squad for their final World Cup qualifiers, but his performance and goal will have done him no harm in his bid to be part of next summer's tournament.
David Gray's side are away to Motherwell on Tuesday before a home clash with Celtic on Sunday, live on SportNews.
Can they continue their push to challenge at the top of the table?
