The Hoops temporarily extended their lead at the top of the Scottish Premiership to seven points.
Ronny Deila's men managed to extend their lead at the top of the Scottish Premiership to seven points - though Aberdeen reduced the gap back down to four points following their win the next day - after a goal from Mackay-Steven and a brace from Patrick Roberts saw the Hoops turn the game on its head following Jamie Walker's early opener for the away side.
And the 25-year-old explained that the way that the Bhoys fought back from a goal down against the side that are sitting as high as third in the division highlights the desire to retain the title within the Celtic squad.
"There's talk from a lot of people who think we're not going to win the title and how other teams are running us close," he told The Scottish Sun.
"Sometimes to win titles you've got to bite and scratch and there was an element of that against Hearts. You saw a lot of tackles flying in and that's just players giving their all.
"It was pleasing to be involved and we showed our title credentials.
"It's games like these where you really need to show you want to win it."
While the 8-1 against Hamilton in January or the 6-0 thrashing of Dundee in September obviously sends a message to title rivals Aberdeen and the rest of the division that Deila's side have the ability to tear teams apart, their current form arguably sends just as clear a message to those sides hoping to catch them.
The team have not played so well recently, but have still found a way to win four games in a row in all competitions, which just proves that even if Celtic are unable to reach the higher gears, they still have the quality to pick up wins and secure the title.