IT is hard to think of another fixture in world rugby that wraps up quite as many themes and sub-plots in one narrative as the inter-city derby between Glasgow and Edinburgh.

When the sides meet at Scotstoun tomorrow evening, the issues at stake will include the destination of the 1872 Cup, a stack of RaboDirect PRO12 points, bragging rights for the rest of the year and, in the absence of the national trial that used to be the festive set-piece, places in the Scotland squad for the forthcoming RBS 6 Nations championship.

Taken together, those factors add a compelling edge to the contest. Taken alone, however, the last of them can only provoke a rising sense of dread among those who watched the fixture's first leg at Murrayfield last week. After their recent wobbles, Glasgow's 20-16 win in the national stadium may have been a timely confidence boost for Gregor Townsend's players, but the psychological effect on the Scottish rugby public at large was more likely to have been a sharp plunge into despair.

Even allowing for the wretched state of the Murrayfield pitch and the understandable edginess of the players involved, the Boxing Day encounter made for profoundly depressing viewing. There was energy and effort aplenty, of course, but wit and ingenuity and basic skills were conspicuous only by their absence. Rarely has Christmas lost its sparkle quite so quickly as it did that day.

The brutal truth of the matter was that some of the back play was execrable. Dougie Fife and Stuart Hogg took their tries smartly enough for Edinburgh and Glasgow respectively but, other than those efforts, it is hard to recall a single backs move that brought spectators to the edges of their seats.

In light of which, it is not particularly surprising to look down the PRO12 table and see that the Scottish sides' combined haul of try bonus points this season adds up to precisely one, collected by Edinburgh against Connacht in November when the Irish side suffered a late and spectacular defensive collapse.

There is no question that we are in an era of famine as far as Scottish backs are concerned. When everyone is fit and firing, as they were in the early stages of the 2013 Six Nations, then Scotland can pose a decent threat, but it only takes a couple of injuries and a slight dip in form here and there to reveal how desperately bare the cupboard really is.

A glance in the history books helps, too. Staggeringly (and justifiably ignoring Chris Cusiter's 2005 appearance in a warm-up moneyspinner against Argentina in Cardiff that was, ludicrously, granted full international status) no Scottish back has played in a Lions Test since Townsend and Alan Tait took to the field against South Africa in 1997.

It is not as if the cream of the crop have been plying their trade elsewhere. In Scotland's November internationals against Japan, South Africa and Australia, the only backs with exile status were Duncan Taylor of Saracens and Max Evans of Castres, neither of whom would be considered first-choice players.

No such problems up front, of course. Indeed, it is remarkably easy to come up with a Scotland pack made up entirely of players from English, French and Welsh clubs. Loosehead prop might be a problem, but Kyle Traynor, now at Bristol (and playing very well according to Andy Robinson) would fill the shirt well enough. Thereafter, there's not much to be said against Scott Lawson (Newcastle Falcons), Euan Murray (Worcester Warriors), Richie Gray (Castres), Jim Hamilton (Montpellier), Kelly Brown (Saracens), John Barclay (Scarlets) and Johnnie Beattie (Montpellier).

You'd be happy enough to have Al Strokosch (Perpignan) sitting on the bench too. If clubs of that calibre are willing to take on those players then all the signals suggest that this is a golden era for Scottish forward play. Except, of course, that it isn't. The signals are hugely misleading.

Yes, the Test side can pick from strength, but Glasgow and Edinburgh clearly cannot. Let's leave questions of eligibility aside, and look instead at what Scotland is actually producing in the way of top-flight forwards. In the starting Edinburgh pack, only two - Ross Ford and Grant Gilchrist - could be said to be the products of the Scottish rugby system. For Glasgow, the number was an only slightly more reassuring three: Pat MacArthur, Jon Welsh and Rob Harley.

Most startling of all was the make-up of the back rows. Of the six loose forwards who started, only Harley had come off the Scottish conveyor belt. Edinburgh's entire back row - Cornell du Preez, Roddy Grant and Dave Denton - had all learned their rugby in South Africa.

Tyrone Holmes, also from that corner of the world, was at openside for Glasgow. Edinburgh's back-row cover was provided by an Australian, Glasgow's by another South African.

None of which is meant to cast aspersions against any of those players. Rugby is a game of open borders these days, and, for the most part, is much the better for it. What is troubling, though, is that Scotland, a country once renowned for the quality of back-row players it produced, appears to be struggling to come up with any. Too many seasons have gone by since a truly outstanding loose forward came to the fore in these parts.

Food for thought for the interim Scotland head coach Scott Johnson as he takes in the inter-city match tomorrow - grateful, perhaps, that he will have handed over the reins to Vern Cotter by the time Scotland play their summer Test against South Africa on Saturday June 28.

As that date falls outside the international Test window, Scotland will almost certainly have to field a team made up entirely of players from Edinburgh and Glasgow.

On the evidence of last week, it is not a prospect to savour.