Heart of Midlothian's unbeaten run in the Scottish Premiership this season was ended by Aberdeen with a 1-0 win on Sunday.

They had won nine of their opening 12 league games and remained unbeaten before being beaten by Aberdeen 1-0 on Sunday.

They are still four points clear of nearest challengers Celtic, who have played a game less, but have dropped points in three of their last four games.

Adding to the growing sense of complacency, they are nervously awaiting the results of a scan on Lawrence Shankland's shin, their leading scorer who missed the Pittodrie defeat.

Parallels are being drawn with Hearts' impressive start and how Aberdeen began last season - winning 10 of their first 11 and maintaining their pace with Celtic before going on to lose 14 games in a row.

Jimmy Thelin's team eventually finished fifth in the Premiership, but beat Celtic at Hampden in the Scottish Cup.

Manager Derek McInnes refused to panic after the loss on Sunday, but does their recent wobble cause any cause for concern?

Based on their performance on Sunday, not really.

Hearts had the better of the play, which was played in terrible weather, spurning several chances in both halves.

Frankie Quinn headed straight to the goalkeeper from a few yards out, Harry Milson blasted wide from close range, Thomas Mikkelsen headed straight to Dimiță Mitov and Claudio Bragia was denied when he had a clear chance to score.

"Hearts can only blame themselves for not getting three points", former Scotland midfielder Michael Stewart said. "They had plenty of chances."

When Aberdeen got their only real chance, they took it. Quinn failed to clear and Topi Keskinen made no mistake, finding the bottom corner.

"I thought we were the better team, created the better chances", McInnes said. "But we didn't show composure or quality in the final third. We looked a bit rushed at times."

"If we scored, it would have been a completely different environment for Aberdeen."

"I thought we did enough today not to lose. I was actually quite encouraged by today's game without Lawrence and Craig Hallet."

"When you lose a game, you have to respond and I'm sure we will respond."

Hearts are "ready to start" the festive run-in.

Hearts have scored more goals than expected this season, with 29 compared to an xG of 22.46, so a more legitimate concern might be that their overperformance won't continue, especially if Shankland is out for a long period.

On Sunday, Pierre Landry Cabore played alongside Bragia and had his moments in his fifth appearance for the club, but wasted his best chance by heading wide.

Despite the loss, former Scotland striker Chris Boyd couldn't see cause for alarm.

"Four wins, that's a slight cause for concern", he said on Sky Sports. "I don't think Hearts had a poor player on the pitch. I thought they defended reasonably well, they just lacked that cutting edge. There was just no forward of the goal."

McInnes' side now travel to Motherwell before a busy December fixture list against Kilmarnock, Celtic, Falkirk, Rangers and their city rivals, Hibernian.

"I don't think it's a terrible run at all", McInnes said. "We have interesting games and games we can win."

"We'll get back to our business and be ready to go again."

"We know who we're playing for, we're enjoying being top of the league. We enjoy winning games more than not winning and it's important we get back to that feeling."

Assistant captain Cammy Devlin echoed his manager's sentiments.

"The best thing is we only have to wait six days for our next game", he said. "It's about not feeling sorry for ourselves - we'd have lost the game."

"Just get back to training, work as hard as you can and turn that feeling of today into smiles and get the winning feeling back."

What did the fans say about it?

Paul: Hearts' bubble has burst well and truly.

Alasdair: Last night's Calum McGregor goal for Celtic seems to be the pivotal moment of the season. That result today seems to confirm that.

Colin: Celtic are back on top for Christmas.

Jimmy: Hearts will be third for Christmas and won't finish higher than fourth.

Peter: Hearts are as vulnerable as any other team. That result will have a big impact on them. A completely different dynamic will be in their bus home without points. They also benefited from some very controversial VAR decisions.

Alan: The defeat had to happen. I'm disappointed but now is not the time to dwell on it. Come back stronger and win the next one.

Rudiger: The only bubble that burst is the one others inflated in our name. 39 out of 30 points is not something to worry about.

Steven: Does anyone seriously think Hearts are title contenders? As Rangers managers from Michael Beal to Phillip Clement discovered, talking big always has the same result - Celtic win the league. It's not easy. I admit if I'm wrong, but McInnes doesn't win trophies and Blyum - undoubtedly talented - is just putting too much pressure on him.