Letting Celtic draw level on points could have been particularly fatal for Hearts considering the reigning champions have three of their remaining five games at home, including a potential final-day title showdown against Hearts, while both their title rivals have two.

There was plenty of tension at Tynecastle as a result, but McInnes hailed his side as they "had to dig deep" for victory.

It is not for the first time.

Hearts have won 13 points from losing positions in the Premiership this season - only Dundee United, with 16, have recovered more.

Amazingly, though, this was their first win in the seven games in which they have conceded the opening goal since 30 August against Livingston - and they will surely take confidence from that.

Emmanuel Longelo had put Motherwell ahead in the 50th minute and the visitors squandered several good chances before and after Claudio Braga levelled.

"There's no two ways about it - we were under the cosh," McInnes admitted. "But I still felt quite calm in the sense I thought we would score. We very rarely don't score, particularly here at Tynecastle."

Indeed, Hearts have found the net in 29 of their 33 games - more often than any other team in the Premiership this season, and one more than Celtic.

"The reaction of the players is magnificent," McInnes said. "It's exactly what you want. Nobody's settling for a draw.

"It says so much about them that they found something just to drag themselves off the canvas again and get the win."

A Lawrence Shankland penalty three minutes from time and a stoppage-time strike from substitute Pierre Landry Kabore secured a first win over Motherwell this season after two draws.

McInnes would "not get carried away" with going into the split still leading the table, but captain Shankland enthused: "It's five cup finals, really, isn't it?

"It'll make for a brilliant end to the season for Scottish football."

Digging out a victory was also O'Neill's theme as his side secured a 13th clean sheet of the league season - albeit that is still less than Hearts.

However, they failed to build on a bright start and Alex Oxlade-Chamberlain's breakthrough after 15 minutes.

"Winning the game was really important, but we didn't play well," said Celtic's veteran interim manager. "I thought the energy levels looked low."

O'Neill suggested that would be understandable if his side were holding on to a lead in the final stages.

"But it set in pretty early in the second half, which is a bit of a concern," he added. "We've stayed in the hunt and, in fairness to the players, they did dig it out in the end, so it was good."

As Hearts head off to sunshine training camp in Spain before the Premiership resumes at the end of the month, Celtic must prepare for a return match with St Mirren in next weekend's Scottish Cup semi-final, with O'Neill promising "to rectify" what he saw go wrong against the Paisley visitors.

'No reason why Hearts can't do it'

Former Celtic goalkeeper Pat Bonner found that lack of energy "a real worry" after a performance that "was not very convincing".

"It was actually St Mirren who were the better team, especially in the second half, when they pinned Celtic back but didn't have that cutting edge," he told BBC Scotland.

"You could see the relief not only around the stadium but among the players."

Former Hearts striker Steven Naismith pointed out Celtic had only had seven goal attempts against St Mirren but stressed that, at this stage of the season, "it was about winning" for all the title chasers.

As for his former club, he added: "Having not been in this position before will be the biggest test for me.

"They are playing the best teams in the league, but they have fared well against the best teams in the league. All to play for."

Former Hearts midfielder Ryan Stevenson felt McInnes' side could easily have found themselves 4-1 behind to Motherwell but suggested: "Somehow, cometh the hour, cometh the men and their big players had to step up. It is a massive three points."

Fellow ex-Hearts midfielder Michael Stewart added: "For Hearts to be sitting top of the table, they are not there by chance, they are not there by sheer luck. They are there through a lot of good play but also mentally showing some real strength.

"And they are going to need that going into the post-split fixtures. I don't see any reason why Hearts can't do it."