After 83 minutes, Celtic were awarded a penalty. Had they scored, and won, they'd have had a two-point lead with a chance to make it five soon after. They'd have been unbackable favourites for the title.

All Georgios Samaras had to do was beat Allan McGregor. He couldn't. Rangers went on to win the title.

Scanning through the years since, it's difficult to find another league game between these two clubs that had so much riding on it as Sunday's renewal at Ibrox.

Celtic lorded it in the years from 2011, but even when Rangers won the title in 2021, it was a procession without jeopardy. Those late-season derbies were big occasions but they were largely meaningless in terms of the destination of the league.

So you can make a compelling case that Sunday's instalment is the biggest Old Firm match in the league in 13 years.

If Rangers lose, it's advantage Celtic. Draw and it's as you were. Win and Rangers go two points clear with a chance to make it five in midweek at Dundee.

That's not an insurmountable gap, but context tells you how tricky it would be for Celtic if that scenario played out.

'Clement has brought hope to Rangers'

Under Philippe Clement, Rangers have dropped only eight points in 22 games. Expecting them to drop five or six in what would be six remaining games is a bit of a stretch.

Clement has won 19 of 22 league games since becoming manager in October. A victory on Sunday would mean that, in the entire history of the Ibrox club, only Bill Struth (21) and David White (22) will have won 20 league games in fewer matches.

They're seven points better off in 2024 than Celtic. In Clement, we are seeing the kind of sure touch that has been, for so long, the exclusive preserve of the manager from across town.

In his short time, Clement has shown the restorative powers of Ange Postecoglou when he took over after the 10-in-a-row-that-never-was and the feelgood energy of Rodgers in his first coming, after the flatlining of Ronny Deila's final season.

The Belgian has brought hope when it was previously thin on the ground. He has revived players who were looking tired and added vitality with some astute new signings.

He's had a battalion of injuries to contend with, but has made light of them.

Abdallah Sima, one of his principal attackers, is only recently back after more than two months out. Danilo, another of his goalscoring options, hasn't played since early December. Others - far too many for his liking - have played bit parts only.

Clement has had one transfer window and he's made hay. Ready-made starters, rather than young project players, have been recruited and put straight into the team rather than deposited in finishing school.

Mohamed Diomande has become a mainstay of the midfield. Fabio Silva has played 10 league games. Oscar Cortes six, though he's been one of the injured ones since late February.

'A manager of action rather than a talking shop'

You couldn't say that Rangers haven't missed a beat under Clement, but the improvement has been rapid and stark.

Some of their performances have been stodgy, but they've shown grit when things haven't been easy. They've dug in.

A less-recognised feature of Rodgers' first two, trophy-laden, seasons with Celtic were the number of one-goal wins (12 in the invincible season of 2016-17 alone). It wasn't all champagne. There was plenty of heavy in there, too.

Rangers have shown a capacity to win ugly, an essential requirement of any team with title aspirations. They're now displaying steel and belief rather than just talking about steel and belief.

Everything goes back to Clement, a manager of action rather than a talking shop.

Too often in the past, Rangers managers, coaches and players have expressed madcap delusions of superiority over their city rivals, a form of collective hypnosis that was surreal to observe.

Clement has brought clarity of message and purpose. He's driven much of the hubris out the door and you get the impression that if any still lurks in the corridors of the training ground he'll find it and get rid of it.

There's a relentlessness about Clement, a refusal to allow anybody to smell the roses until the job is done. Every time he's asked to project too far forward, he repeats his mantra. Next game, next game, next game. Right man, right place, right time.

But we're entering a different realm now. The home straight is in sight and that can do strange things to a team's psychology.

The prospect of becoming champions is real for Rangers for only the second time in a dozen years. There's an excitement and a pressure that comes with that.

You can hang your hat on Clement staying cool, or what constitutes cool on such a day. But in the heat of Sunday it's the amount of ice he's managed to put in the veins of his players that will count.

He's done so much in such a short space of time, but the biggest test of his mettle, and the mettle of the team built in his image, is upon him now.