The crown jewel of the Scottish football calendar, the Celtic vs Rangers derby is one of the most iconic in world football, always attracting attention from fans around the world. If you thought the previous fixtures this season between the two sides meant a lot, then you haven't seen anything yet.

This Sunday's match at Hampden in the Scottish Cup semi-final has more at stake than usual. The Hoops are going for a famous treble of trophies and also an unbeaten domestic season. The Gers are aiming to stop their great rivals from achieving that feat and also to take a first step towards success in the Pedro Caixinha era at Ibrox.

Celtic have won three of the four fixtures so far this season, starting with a 5-1 thumping at Celtic Park. Since then the Gers have gradually fought their way back, first to a 1-0 defeat, then actually scoring against them in a 2-1 defeat at Ibrox before eventually holding them to a draw last month.

Is it Rangers' time to finally pick up a massive derby victory against Brendan Rodgers' team?

Celtic are still the favourites but here are three reasons why the Hoops can't underestimate their city neighbours...

Unbeaten under Caixinha

Since Pedro Caixinha came into the Ibrox hot-seat there has definitely been a lift in optimism surrounding the Light Blues. Initially beating Hamilton before poor draws against Kilmarnock and Motherwell, the Gers are going into the game at Hampden off the back of two consecutive wins over Aberdeen and Partick Thistle.

In fact, their form over the last six matches in the Scottish Premiership is the same as Celtic's with three wins and three draws each.

The Hoops have taken their foot off the pedal a little since wrapping up the title and although still undefeated, draws against Partick Thistle and Ross County have rung a few alarm bells ahead of the semi-final showdown.

Has the edge come off their game? Can the Gers replicate the draws of both those teams and force the game to the lottery of extra-time and penalties?

The draw at Celtic Park

Without a doubt, Rangers' draw at Celtic Park will have been a massive confidence boost to the Gers squad who at some points this season must have wondered if they could ever best the Hoops.

It will have shaken the Celtic support a little too. Ultimately the game meant nothing but if the match at Hampden follows the same pattern as March's fixture then progression to the final may be a little too close for comfort.

A draw across the 90 minutes would be enough to force the fixture into 'anything can happen' territory, as we saw last season when a dramatic extra-time culminated in a penalty shoot-out that Rangers fans will never forget.

The thumping of Aberdeen

Perhaps the biggest indicator Rangers are making progress under Pedro Caixinha was their recent thumping of Aberdeen at Pittodrie, a match that Derek McInnes' side went into as hot favourites.

The Dons dominated most of the match but failed to take their chances and in the closing 20 minutes, the Gers showed a ruthless edge that has been missing for the majority of their season.

If Celtic turn up to Hampden slightly below par then Caixinha's side could be well placed to rise above expectations again and turn the semi-final into quite the battle. The Light Blues are arguably at their best when they are underdogs and that's certainly the case this weekend.

The hero of Pittodrie, Kenny Miller, always loves these occasions too and if he's in the mood this Sunday then, frankly, anything can happen.