IT was former Tory leader Iain Duncan Smith who coined the phrase "never underestimate the determination of a quiet man" but it could just as easily apply to David Marshall.

While it was his Celtic contemporary Artur Boruc, and not Marshall, who visited the manager's office at Parkhead frequently during Gordon Strachan's time there, it is somehow typical that the 28-year-old Glaswegian should have stealthily put himself in the box seat for the Scotland No 1 role, at least while Allan McGregor is injured.

Although Blackpool's Matt Gilks and another member of Strachan's one-time Celtic contingent, Scott Fox, are also in the squad for the upcoming friendlies against the USA and Norway - the first of which takes place at Hampden on Friday -a snapshot of last weekend's fortunes in the Barclays Premier League alone illustrated how far Marshall has come.

While Boruc was allowing a punt from his opposing goalkeeper Asmir Begovic to pass directly into his net from the length of the pitch after just 15 seconds, the Cardiff City man was confirming his ever-improving reputation with a clean sheet in the first ever top-flight South Wales derby. It is all a far cry for a man whose Parkhead career never effectively recovered from the nine goals he shipped in Strachan's first two matches in charge, against Artmedia Bratislava and Motherwell.

"When we were at Celtic I don't think I ever saw David in my office, whereas Artur Boruc had his own chair," Strachan said. "And sometimes I felt like flicking the switch on it… but what David has now is almost like an aura. It's indefinable and it's nothing to do with how noisy you are. The Cardiff players will stand in the tunnel now, look at him and think, 'I'm glad he's with us,.

"I had David at Celtic when he was a young man and he's a very quiet individual. He had everything but seemed to lack a personality once he walked on to the pitch. But he's found that personality now. He has developed his character. It isn't a demonstrative one but it says, 'I'm all right, I can deal with this. Fling anything at me - I'm fine.'

"He's a Premier League goalkeeper now and he deserves that status. He could easily have hung on at Parkhead, done the usual thing where players hang on for five or six years and their career goes backwards. They become a domesticated animal and, when someone eventually chucks them out into the wild, they think, 'What happens here?'. Too many Celtic players didn't want to go out on loan but David wanted to play. He had to be transferred because he was too good to go out on loan."

Scotland climbed 28 positions on the Fifa rankings table between September and October - "I pay a lot of attention to the rankings when we're moving up them," the manager jokes - but the Scots may still have their hands full against an American side who are 13th, with participation in their seventh consecutive World Cup finals already secure.

Like Walter Smith before him, Strachan has mixed feelings about the worth of international friendlies in general, but any reservations are swiftly overcome by the box office appeal of a meeting with the USA and Jurgen Klinsmann, a man whom he admires as a player and manager. From his playing days, Strachan particularly remembers a 3-1 Coventry City victory at White Hart Lane against Klinsmann's Tottenham side when the East Midlands outfit were fighting for their top-flight lives in 1992/93.

"I was player-coach and it was one of these games where we had to win to stay up, and we did it so that was a good night. He was very intelligent and I always found him a great lad, even if people used to go on about his diving."

As a manager, Klinsmann deserves credit for introducing young players like Bastian Schweinsteiger and an up-tempo way of playing while manager of Germany.

"That young German team which kicked off five or six years ago was exciting to watch although they have grown since then," Strachan. said. "He was brave in his decisions. He left out players with experience in favour of younger ones and that has been beneficial. If you speak to people involved with the USA, it is hard, hard work they put in. That is what he did as a player and it didn't do him any harm, because he was still running after 90 minutes."

As much as Strachan is at pains to stress the competitive nature of the friendlies, there will be room for limited experimentation, with Gordon Greer of Brighton and Derby County's Craig Bryson likely to be rewarded for their attendance and application at training.

"I think they deserve a wee bit for what they are putting into training," Strachan said. "A couple of days before a team is announced, you can maybe sniff what might be coming and it has never affected them. "I asked the SFA 'do we play these friendlies for money?' and the SFA were like 'no'."So if we are not playing them for money, you have to decide if it is worthwhile doing these games - now and then a good training session would suffice. But there is a sparkle to this one. Jurgen Klinsmann is bringing them."

Tickets for Scotland v USA are just £5 for kids and from £12 for adults. Visit www.scottishfa.co.uk or call 0844 875 1873.