Rugby might still cling to its old boast about being a game for all shapes and sizes, but more and more Scottish coaches are finding they have to cast their nets far and wide to find the shapes and sizes they need. Glance down the team sheet of a typical Scottish club and you could well find the name of a player from Bucharest or Buenos Aires alongside those from more traditional rugby nurseries. For years, there has been a healthy traffic of talent between Scotland and the Antipodes, but clubs are now scouring some more improbable corners of the globe as well to fill the gaps in their sides.

In the past few weeks alone, the Scottish Rugby Union's player registration department at Murrayfield has processed the details of players from Sweden, Spain, Italy and Romania. Glasgow and Edinburgh might grab the headlines with their big-name overseas signings, but Scotland's amateur and semi-pro clubs are starting to look increasingly cosmopolitan as well.

And the foreign legion is being swollen, in every sense, by the number of props coming in from abroad. The widespread recruitment of fat blokes might seem ironic in a country that is meant to be suffering an obesity epidemic, but one players' agent confirmed that the front row is the area that most clubs are desperate to fill.

"It's funny how it has changed," he explained. "I used to get a lot of requests from clubs looking for stand-offs because they thought that's what made a team tick. Now, it seems that they all appreciate the importance of the front row, and tighthead props in particular, to give their team a solid platform."

The evidence supports his claim. At Ayr, the No.3 shirt has recently been worn by Denford Mutamangira, a Zimbabwean international prop, although he will be packing down at loosehead in this weekend's match against Melrose. The first-choice tighthead at Jed-Forest is Alex Croituru, a Romanian. Selkirk also have a Romanian prop, in the substantial shape of Catalin-Andrei Graur, a former under-20 internationalist. Hamilton's scrummaging cornerstone is Gaston Ibarburu, a Uruguayan Test player.

This at a time when Scotland probably has its best crop of home-grown international tightheads for many years. You would have to go back a long way to find three players of the calibre of Euan Murray, Geoff Cross and Moray Low all competing for the Test berth at the same time. Alarmingly, however, there is an impression among Scotland coaches that the conveyor belt of talent that produced those players could be grinding to a halt.

Why? The fingers are being pointed at the age-grade law variations which have depowered the scrum at under-18 level. For younger players, the scrum is essentially nothing more than an uncontested restart, while there are strict rules concerning the set-piece for older teenagers.

As the scrum is not allowed to move more than 1.5 metres, it is virtually impossible to push a side off its own ball – so teams don't even try. Similarly, the engagement process has none of the ferocity of the adult game. The strong, squat players wanted at senior level are simply not being developed by the junior game.

"I think we've obviously suffered a bit over the last few years from having non-competitive scrimmages," said Dale Lyon, the Hamilton coach. "If you take the competitiveness out of scrummaging at junior level it can give a false impression of how good a player might be. A lot of players simply aren't ready for the physicality of playing senior rugby with full scrums."

Lyon was instrumental in bringing Ibarburu to the Lanarkshire club. Initially, Hamilton had been looking at a prop from Cameroon, but that deal fell through due to visa issues. Lyon has no problem with the idea of importing players, but he sees it as a developmental exercise rather a matter of short-term expedience.

"What we want is players who can complement and help the growth of our own players," he said. "Some people bring in players because they want to win things and think that certain individuals will make that difference, but I would rather bring in players who can add something and hopefully develop the talent we have in our local area.

"But there is definitely a shortage of front-row players within Scotland. You'll see that through the season, with the number of games that go to uncontested scrums at second and third team level. A number of games are being called off because of a lack of front-row cover. It is a worrying trend, but we want to look at developing our own players into being front row players too."

Selkirk coach Brian Cassidy echoed Lyon's concerns about the lack of talent coming from the junior ranks. "The big problem we find is that the laddies come up here and you have to start from scratch with them," said Cassidy. "You can have a young prop who is dead keen but it's difficult to ask him to do a man's job so you have to look elsewhere to fill the position.

"Don't get me wrong. I understand the need for health and safety. But these boys come up to senior level when they are 18, they get put into the seconds and it's a completely different world. Some of them just don't have a clue what they're doing.

"What they do until they are 18 is not scrumming as such. My worry is not so much that they are not learning how to scrum, but that they are not learning how to get out of trouble. That's my concern. They can come up against a prop who is maybe in his 30s or 40s and who can put a young lad into a situation that he can't get out of."

In truth, the emphasis in Scotland's game has always been on forward mobility. With a few notable exceptions – Murray and Iain Milne spring to mind – it has never been a nursery for the sort of immovable objects that countries like England and South Africa have traditionally turned out in droves.

And Selkirk, according to Cassidy, is Scotland in miniature. "Our biggest problem for years in Selkirk was that we couldn't compete up front," he said.

"We always had good backs, because size isn't such a bit concern there, but we struggled to get the ball. There was no lack of spirit, just a lack of size."