Three and that's the magic number... or it most certainly wasn't for Celtic and Ange Postecoglou this time around.

Postecoglou was appearing in his third consecutive Hampden Park appearance but his side was denied a third consecutive win in a third consecutive Glasgow derby match.

A goal from the number three Greg Taylor looked to have kept Celtic on course for the domestic treble but goals from Scott Arfield and an own goal from defender Carl Starfelt in extra-time handed Rangers a narrow 2-1 win at the national stadium in the Scottish Cup semi-final.

On Easter Sunday it's usually all about the most important deity of all who rose again on the third day and all that. The Greek-born Australian had fast become something of a God in Glasgow's east end in just nine short months.

For once, though, his men failed to rise to the occasion as their city rivals booked a place in the end-of-season showpiece against Hearts on May 21.

The pre-match hype from a Celtic perspective was whether goalscoring talisman Kyogo would feature from the start. Postecoglou put everybody out of their misery some 75 minutes before kick-off and the Japanese striker had to be content with a place on the bench.

The national stadium still crackled with a sense of anticipation for the fourth Glasgow derby encounter of the season.

It was going to be nothing less than a war of attrition in the Mount Florida bowl. No quarter was asked and none was given in a first half that was as scrappy as they come. It was perhaps summed up by John Lundstram's thumping challenge on Celtic skipper Callum McGregor. Blood, guts and thunder - or, to borrow a phrase from the late, great broadcaster and journalist Jimmy Sanderson - it was "all perspiration and no inspiration".

READ MORE: Celtic 1-2 Rangers (after extra-time) - Carl Starfelt own goal decides epic Scottish Cup semi-final

The game was crying out for a hero and the Celtic fans then went crazy on 57 minutes as Kyogo and Matt O'Riley entered the fray for Tom Rogic and Matt O'Riley. Could they provide the vital spark for Postecoglou's men?

The divine intervention came from the most unlikely source. Full-back Greg Taylor, so often a whipping boy for the Celtic supporters, slammed a low 14-yard shot via a deflection into the bottom corner of the net before taking off like a rocket to celebrate among the throng of fans gathered behind the goal.

Cameron-Carter Vickers then smashed one off the crossbar as Celtic came within inches of a second goal moments later but the mood inside Hampden noticeably changed when Scott Arfield thumped home a superb leveller for Rangers in 79 minutes to make it 1-1.

Neither side could find a normal-time winner but it was Fashion Sakala - helped by a deflection - that settled the match in the end.

The number three is considered the perfect number. It is the number of harmony, wisdom and understanding.

It is also the number of time – whether that be past, present and future; birth, life and death; beginning, middle and end.

Three also denotes divine perfection. Postecoglou and Celtic may not have scaled the heights of divine perfection with Celtic yet but the remarkable success story this season has surely only been halted temporarily with their first defeat in 34 domestic matches.

Postecoglou and the supporters will feel that they are merely at the beginning of a journey. The treble bid was blown to smithereens as the hat-trick of domestic trophies eluded the Aussie this season.

He can no longer emulate the feats of former Celtic bosses Martin O'Neill and Brendan Rodgers by completing a clean sweep in his first season at the helm.

But he still remains on course to win the league title as they hold a six-point cushion with five games remaining in the campaign.

Was this a wobble? Who knows. 

As for Postecoglou, he will need to pick his players back up for the title run-in and prove that he has been imbued with De La Celtic Soul. No more, no less.