THE old saying goes that the league is always the bread and butter of any football club's season.

But with Rangers' seemingly invincible march on the League One championship having made the third tier title's destination a foregone conclusion before the earliest Christmas card was penned, one of the game's oldest clichés has for once proven less than totally accurate.

The Ibrox club's only available avenue for a pop against the best, in a domestic context, remains the Scottish Cup.

And now former Gers' Seventies and Eighties fans' favourite John McDonald has no hesitation in heaping extra significance on the Govan side's hopes of mounting a strong challenge in the Scottish game's blue ribbon knock-out competition.

Former lethal strike weapon McDonald made 230 appearances for Rangers between 1978 and 1986, scoring 77 goals and winning the 1981 Scottish Cup and the Scottish League Cup in 1982 and 1984.

He has no doubt that if Rangers dispatch Dunfermline for a third time this term in their fifth-round encounter at Ibrox in 13 days' time, the motivation to mount a charge all the way to a final that will be played at Parkhead would prove irresistible to both the Rangers' players and the red, white and blue legions who would march on the East End.And the still sprightly 52-year-old is confident that the string of former SPL players signed by Ally McCoist last summer will all crave the chance to prove a point against former top-flight adversaries - should Jim Jefferies' boys once again be overcome.

McDonald said: "I guess with Rangers being 20 points clear in League One, you have to say that the Scottish Cup campaign has taken on a lot more significance this season.

"On top of that, Rangers went out of the League Cup comparatively early without getting a crack at a Premiership side, so the Scottish Cup is potentially now the only chance to get for something like that, should they get past Dunfermline.

"Ally McCoist has made a good few signings from the old SPL with the likes of Jon Daly, Nicky Law, Ian Black, Dean Shiels, David Templeton and Stevie Smith all in the squad.

"These guys have all played their part in helping the club do what it had to do first, which was get to the top of League One and build a pretty much unassailable lead.

"But now the fans want to see how they will do against an SPL side and the only shot at that is in the Scottish Cup.

"Rangers are going to take nothing for granted in terms of the Dunfermline game, but on the balance of what has gone before they have to fancy themselves to do that.

"If they do then I would imagine some of the boys signed from SPL clubs last season I have just mentioned would love the chance to prove they can still more than hold their own against Premiership opposition.

"So the Scottish Cup, for me, has taken on added importance this season. No question about it."

McDonald has no doubt about the dream scenario for Gers' Scottish Cup hopes. The pint-sized one-time Ibrox poacher said: "If they can get past Dunfermline and then land a home draw in the quarter-finals, against any club other than Celtic, I think they would fancy their chances.

"Then, of course, the semi-finals are at Ibrox and you have the final at Parkhead. Rangers have already won a Scottish Cup at Celtic Park, back in 1993, when they beat Aberdeen 2-1, and a repeat of that victory would go down very nicely. But it is interesting when you look at the fifth-round draw just how few Premiership teams are still left in the tournament.

"Motherwell were the big casualties in the previous round to Albion Rovers.

"Then you have got two all-Premiership ties with Celtic hosting Aberdeen and Dundee United entertaining St Mirren. Outside of those, you have to think that Inverness should win at Stranraer while Hibs will be favourites at home to Raith Rovers.

"So in the last eight there will be a 50% chance of a draw against a team from outside the top flight. That could make the quarter-finals very interesting indeed."

The other huge element of spice in any quarter-final draw, should both halves of the Old Firm make it into the last eight, is Rangers' readiness to face their most ancient rivals Celtic.

McDonald was brutally honest in his assessment of such a possibility.

The former Gers' marksman said: "Right now, I don't think Rangers do want Celtic.

"You look at the comparative revenue streams of both clubs and Celtic are talking about signing a £6million player and Rangers might have to lose some of the present squad.

"That is the reality of the present situations both clubs are in and it is heavily weighed in Celtic's favour.

"That said, any Old Firm derby is won by the side that turns up on the day. In a one-off, in the Scottish Cup, Rangers would have a side out that would absolutely bust a gut against them.

"So an Old Firm draw would definitely provide the current season with a sting in the tail for both clubs and be great for the Scottish game."