Having started and finished his playing career in the Hoops, and rejected coaching opportunities elsewhere since a knee injury prematurely curtailed his on-field exploits, McStay will don the green and white once more on Sunday night.

He has been tasked with coaching a Celtic side, including brother Willie, in the Scottish Masters at Glasgow's Braehead Arena. It will be an emotional reunion of club and erstwhile captain, as McStay's old boys plot the downfall of Rangers, Aberdeen and Hearts.

McStay and Celtic, through one of the thinnest periods in the club's rich history, were inextricably linked. To have played for another team would have been akin to football adultery.

And he can see parallels today in current Rangers captain Barry Ferguson, who also has expressed a desire to commit his entire career to his beloved club.

Offers for Ferguson will abound, as they did for McStay a decade and more ago, with clubs in England and on the Continent seeking to separate a Scottish international midfielder from his roots.

But as the 36-year-old and his wife await the arrival of child number six, McStay believes the Rangers No6 can flourish close to the bosom of home.

'Barry's love of the club will keep him at Rangers,' said McStay, who has spent the four years since retirement on business interests and with the players' union. 'Anyone who has come up through the ranks at Celtic or Rangers knows there are few more enjoyable theatres in which to play football.

'There are not many places in the game with the same atmosphere as Parkhead or Ibrox, and it would take something special to take Barry from Rangers. He is an outstanding player who has acquitted himself well in the Champions League and with Scotland, especially against England at Wembley where he showed his quality.

'Rangers, obviously, will want to keep him because of those performances in the Champions League, where he was tested against top-quality teams.

Despite exposure at an elevated level these past months, Ferguson ended his first season as captain without a single piece of silverware. McStay can empathise with the plight of Ibrox's young pretender, having laboured in the shadow of Rangers while leading Celtic.

But, equally, he can relate to the -bond which ties Ferguson to Govan and acknowledges it is a relationship which might never be broken.

'Barry has grown in stature in recent times,' added McStay. 'And he will be happy as long as he is getting the challenges to satisfy him. Throughout my career, I had new challenges. I'm thinking back to the European Championships at Sweden 92, when we came out well performance-wise against Germany and Holland, the reigning World and European champions.'

'As long as Barry continues to set the same challenges, with Rangers in the Champions League and with Scotland internationally, he'll be content. You really enjoy the pressure of captaincy. It's an honour and it's something you just can't refuse.'

Having watched Rangers in Champions League this season, McStay is eagerly anticipating Celtic's return to the competition next term. He found himself unable to watch the team for eight months immediately after retiring, such was the magnitude of the mental torment his injury had induced.

But now he regularly joins 60,000 fans at Parkhead, and has been mightily impressed by strides taken under Martin O'Neill this past year.

'It was hard for me to adjust at first, having given the best part of 20 years to totally focusing on football,' he said. 'Eventually, you do learn that there's more to life than training every day and playing on a Saturday.

'Through Tom Boyd's testimonial, I've kept in touch with the lads and I ' v e been delighted. No-one expected the speed of the turnaround. The fans would not have been disappointed if Celtic had simply grabbed a bit back this season, but Martin has really made his mark.

'What every fan now wants is to keep that hold on the domestic game and begin to look towards Europe.'

Whether McStay has gleaned any tips from O'Neill ahead of his coaching bow was kept a closely-guarded secret as he promoted Sunday's six-a-sides with former Old Firm foe Mark Hateley.

Having lost all their games at last year's inaugural event, McStay - whose team also includes several Double-winning team-mates from 1988 - is desperate to lead Celtic to the national finals at Wembley.