If there was a sub-text to yesterday's Scotland squad announcement for this summer's tour of South Africa it was that international contenders are increasingly going to be called upon to show that they have something special in their armoury.

Admittedly Nick De Luca and Max Evans, two of the players who are considered to have what is jargonistically called the X factor, have been left behind. However, as was pointed out by Scott Johnson, the SRU's new director of rugby, both have had ample opportunity at Test level and, to different degrees, have only shown sporadically that they can be game-breakers.

Both have had intermittent injury problems so will benefit from a full off-season, their absence leaving room for the Glasgow pair Peter Horne and Alex Dunbar, as well as the apparently versatile Saracens back Duncan Taylor, to show off their skills.

Elsewhere in the back line, Greig Tonks, Edinburgh's player of the year, fellow full-back Peter Murchie and his Glasgow team-mate Tommy Seymour have also done enough this season to merit consideration.

Among the rest of the backs Tom Heathcote may have won a cap last autumn, but those few minutes against Tonga render him no more experienced at this level than the uncapped brigade.

In the pack, there was a further clue to management's desire for players who have something extra to deliver when the explanation was offered for Tim Swinson being preferred to Tom Ryder, his fellow Glasgow Warriors lock who was capped on tour last summer.

"The sheer cold facts are that Tim's performances have been better than Tom's," he said. "That is how I viewed it. He is abrasive and we like that. We need to find out if that will work at international level as well. I think he has done all the things right and has earned his spot."

In short, players need to bring more than industry alone, which goes some way towards explaining why the relentlessly hard worker that is Rob Harley has been left out in spite of having time on his side as well as having demonstrated versatility. On that note, Johnson also went some way to acknowledging that failing to field a specialist openside flanker had been damaging for Scotland.

"What I don't want to happen is that we go across the other side of the world and bump against sides that are pretty strong and not have a No.7 [openside] under my belt," he said. "I felt that if Al Strokosch had got hurt then I would have moved Kelly [Brown] to six so there was no point in Rob coming and standing there holding tackling bags when he could have had a really good off-season.

"John Barclay's form is good and he warrants his place so that is the right thing for the squad and it allows him [Harley] to have a really good off-season and put on a bit of weight. Kelly and John will go as the sevens but if Kelly got a knock then I didn't have anyone else I felt could compete against these guys physically as a seven."

Dave Denton, though, is once again given a chance because he brings something a bit different.

"He [Denton] has got qualities that we don't possess too much of in Scotland," said Johnson. "He is big and abrasive and an athletic ball carrier but he has also got a naive side about his rugby. I felt it would be more beneficial to take him against other abrasive sides and see how he goes.

"He is important for us going forward and we need to get the best out of him because not many sides around the world have a 6ft 5in, explosive, 117 kg No.8 and that is a pretty good place to start."

It is slightly different in the front row where Pat MacArthur may hardly be a youngster at 26, but is very much so compared with the other uncapped hooker who is travelling. In typically graphic fashion, Johnson suggested it sometimes takes longer for qualities to emerge in that particular department. "It sounds a ridiculous thing to say but there is a man in there," he said of Stevie Lawrie. "He is an impressive bloke. I like that quality, especially in that position. it is not the most comfortable position to play your sport in. He has been impressive in his role at Edinburgh and there is leadership in him. He has been putting a lot of pressure on Fordy. I think this is an ideal opportunity to find out about him.

"An old coach used to say to me that great props don't develop until they have seen their own arse. That takes a bit of time and it is no coincidence that they get better when they mature because they are up against strong men and sometimes it is about technique, sometimes it is about other things. Maturity is a big part of that position."