THE Scottish Cup is officially sponsored by William Hill these days but the fourth round might as well be brought to you by John Robertson.

Not only did he manage both Ross County and Inverness Caledonian Thistle, who meet in Dingwall on Saturday, but the Hearts legend who was brought up in a Hibernian-supporting family also knows a thing or two about Edinburgh derbies, such as the one which takes place at Easter Road on Sunday. "I am working for the BBC on Saturday and going on Sunday so it is a double dose of derbies for me," he said. "I'm going for the away teams both to win after replays because Hearts need the money . . ."

It says something for the exponential growth of both Highland clubs in recent times that Saturday lunchtime's encounter at the Global Energy Stadium should be granted equal billing with the re-match of last season's final. Robertson, who spent five months at the Dingwall club in 2007, having previously guided Inverness to two Scottish Cup semi-finals in successive seasons, knows that some within the Scottish game will always regard both outfits as something akin to Highland hillbillies, but the truth is that the north is an emerging powerbase in the game.

In terms of bang for their buck, that a combined population in the region of 65,000 can support two Clydesdale Bank Premier League teams is quite something. "For years, people in the central belt and the cities have looked at the Highland teams as country bumpkins, their country neighbours so to speak," said Robertson. "But they have proved that they are not that, they are good, honest football teams who can play, and you take them lightly at your peril.

"Geographically, that is always going to be the way it is. For years people have spoken about Aberdeen fans in relationship to sheep and Inverness and Ross County will always be labelled with this country bumpkin, out of sight, out of mind thing; that is just the football banter aspect of it. But there are maybe half a dozen boys in both teams who are from the area, and a lot of boys from the central belt who have ended up at Ross County and the same at Inverness.

"Terry [Butcher] has now brought a good seam of players from England and Ireland and they have brought experience. The football is improving and the young lads in the youth teams are where the biggest change is coming. They are playing against the big teams and learning fast and I think Inverness and Ross County can go from strength to strength."

There is no sense of hyperbole in regarding this as the biggest Highland derby ever, and a meeting of two teams who both deserve to be considered potential winners of this competition. Victory in Dingwall for an Inverness side who sit second in the table after consecutive wins at both Celtic and Aberdeen – amid a run of one defeat in 13 – would complete what would be the finest sequence of results in the club's history, while it wasn't so long ago that Ross County ambushed Celtic en route to reaching the 2010 final.

"Of course these two teams can win the cup," Robertson said. "You just have to look at their results. Given their resources, Celtic will always be favourites, but it took a 92nd-minute equaliser for Celtic to get a point at Dingwall and Inverness have already gone down and beaten Celtic on their own patch. Unfortunately, after Saturday, only one of them will be able to win it this year, because one of them is going to go out."

A crowd approaching 7000 will cram into what Robertson calls "a mini Tynecastle" for a derby that is as fiercely contested as any Robertson has known, but lacking the bitterness present in the Edinburgh and Glasgow affairs. There is a steady cross pollination of players between the clubs, and even a floating support which can be persuaded to watch either club at home.

"There is a rivalry, but not a bitter rivalry," explained Robertson, whose only direct experience of the fixture was a pre-season 'friendly'. "People are quite laid-back in general up there but not when it comes to supporting their teams. They all know each other so it will be a proper derby. Families will go together to the game, split up for the match and go home again. Both teams and their boards get on very well and that shows. But it will be a fierce cup tie.

"In the short period of time, this is the biggest ever Highland derby. I was talking to Graeme Bennett [former Inverness player] and he can't recall the two meeting in a cup game like this, even in the old days. Inverness are on a fabulous run of form and, if they were to beat County, it would be the best three back-to-back results in their short history; a stunning week. And who is to say Terry's guys won't do it. They will be favourites and rightly so, but there's no way it will be one-sided. It will be a fabulous atmosphere and the perfect game to kick off a wonderful weekend."