When you think of legendary managers making a triumphant return, Martin O'Neill's second coming at Celtic is writing a story for the ages. Following their emphatic derby victory over Rangers, it's time to hand the man a ceremonial 'key to the door'—the traditional gift for someone celebrating their 21st milestone.

Of course, honorary entry to Parkhead might have already been secured after O'Neill's first spell in the early 2000s, when he delivered three league titles, two agonizing near-misses (by a single point and a goal respectively), and that unforgettable UEFA Cup final in Seville. But if not, that key may soon be presented, because O'Neill has steered Celtic to within three seismic games of what could be the most unlikely league and cup double in the club's entire history.

Let's pause and reflect on the numbers. Twenty-one years after he thought he'd bid a permanent farewell to Glasgow's East End, the 74-year-old Northern Irishman has just celebrated his 21st Premiership game of this remarkable season. And the stats are nothing short of breathtaking: played 21, won 17, drawn 2, lost 2. That's 53 points from a possible 63—an 81% win ratio.

To put that in perspective, Derek McInnes has had Hearts sitting pretty at the top since late September, but his win rate sits at 64% (admittedly from a larger sample of 36 games). Interestingly, that's the same percentage as Danny Rohl at Rangers, who has 18 victories from 28 Premiership games since arriving in October.

Now, let's imagine O'Neill gets the two wins he needs to overtake Hearts at the summit and snatch victory from the jaws of defeat—a scenario that echoes the drama of 1986. If he does, his total points tally across two spells would be 59 from a possible 69 in 23 games. In other words, in just 60% of Celtic's season, O'Neill would be responsible for a whopping 72% of the club's points.

One can only wonder how much easier things would have been had the board not asked O'Neill to vacate the hotseat for Wilfried Nancy's chaotic month-long experiment. But as it stands, the numbers don't lie: Martin O'Neill's contribution is nothing short of monumental, and the key to Parkhead may soon be his for keeps.