Few outsiders are better qualified to assess the 'Battle of Britain' than the former Northern Ireland defender. Since leaving Elland Road last summer clutching a championship medal, McClelland has twice been on a losing team against Rangers in his capacity as player-coach to St Johnstone. He also watched the Ibrox side win 5-1 at Perth a fortnight ago.
A foot in both camps dictates diplomacy. Nevertheless, McClelland has 'an inkling' Leeds will prevail in what he describes as Britain's biggest-ever club match. 'There's little to choose between the sides,' he said. 'But I've worked with Leeds so I know the quality they're capable of producing. I'm surprised they're not doing better, though they dominated the last two Stuttgart games with the power football they excel at.
'It's hard to judge exactly how good Rangers are. Whereas there are several easy matches for them, no one in England goes out and wins away fixtures by four goals. When we won the title at Leeds, every game was a battle, and that could stand them in good stead for this tie. There again, Rangers will probably come to it fresher.
'Howard Wilkinson, who I rate the best manager in the business, impressed me as an astute tactician. I suspect he might play a rather different team at Ibrox than at Leeds. Whoever wins, there won't be much in it, even though Rangers have been scoring a lot and Leeds have let in more than usual.'
Only two players, Ally McCoist and Ian Durrant, remain at Rangers from McClelland's three and a half years there in the early 1980s. He recalls that Aberdeen, inspired by Gordon Strachan, were then 'running amok' in Scottish football.
His memories of Ibrox reveal the scale of the changes during the Graeme Souness era. 'There was no real ambition. It was all very petty-minded, with very low pay. We weren't a good side, and any player whose contract was up just left.' McClelland did precisely that, going to Watford in 1984.
In his final appearance, Rangers beat Internazionale 3-1 at home after losing 3-0 in Milan. 'I played centre-forward,' he said. 'No wonder it was my last match]'
In 1989, he joined Leeds on the same day as Vinny Jones. He outlasted the tattooed trundler, but was transfer-listed and in the reserves when injuries to the right- back, Mel Sterland, and the centre-half, Chris Fairclough, enabled him to prove his enduring versatility last season.
Had he stayed, the sprightly 36- year-old might well have played tomorrow in view of Wilkinson's defensive problems. However, McClelland is not displeased that containing McCoist will be someone else's worry. 'I know all about 'Coisty', though I still can't stop him. The great thing about him is that he's not afraid to miss. He doesn't hide, but keeps coming back for more.
'When St Johnstone played at Ibrox on the first day of the season he had a terrible game, and was getting stick from the bench. Then he stuck in the only goal of the game with five minutes left.'
Leeds will underrate Scotland's top scorer at their peril; likewise Rangers with Lee Chapman. 'Chappy' is not so pleasing on the eye, but he's a very effective finisher and knows how to move defenders around.'
Yet he pinpoints midfield as the area in which the tie will be won and lost (ironically, Rangers' line-up will include the Leeds-born Stuart McCall, a staunch United fan, while the opposing captain Gary McAllister is, according to McClelland, a 'self-confessed bluenose').
'Leeds have great flair and balance there, and the Scottish boys will be bursting to do well. Rangers have also impressed me with their free-flowing movements, particularly Trevor Steven. David Batty will have a vital role in breaking up those movements and stopping the service to the strikers. Batty is also underrated outside the club. I've a feeling he won't be too popular in Glasgow after these games.'
When Leeds last played in the city, 136,000 roared Celtic to victory at Hampden over Don Revie's side. The prize then was one game: the European Cup final. This time a place in the league stage of the competition is at stake, worth millions in receipts and television rights, which is why McClelland maintains there has never been a bigger match.
He fears that the quarter-finals may be as far as Leeds or Rangers go: 'The way the English and Scottish leagues are set up, the sheer number of games, is not conducive to our clubs doing well in the round-robin format.'
But that, he added in eager anticipation, will be the furthest thing from the players' minds this week.Reuse content