Rangers v Celtic: The key issues before season's fourth Old Firm game

It might no longer mean anything in terms of the title race, but when has an Old Firm game ever been meaningless?

Rangers host Celtic on Sunday looking to repeat their Ibrox derby win earlier in the campaign and finish the season with a Scottish Premiership record of two victories and two defeats against the champions. But what are the key issues around the contest?

• Celtic don't need pat on back - McGregor

• Pick your combined Old Firm XI

Defoe or Morelos?

Rangers have scored more goals than any other side in the top flight this term, with Jermain Defoe weighing in with eight of their 79 efforts since signing on loan from Bournemouth in January. Indeed, the former England international has the best scoring rate in the division with 0.8 goals per 90 minutes.

The 36-year old has three strikes and three assists in the five league games since replacing the suspended Alfredo Morelos. So good has his form been that he was preferred to the Colombian talisman against Hibernian last weekend despite Morelos being available after his ban.

Can Edouard continue stellar streak?

Odsonne Edouard will likely lead the line for Celtic and the 21-year-old has a stellar Old Firm record, with four goals in five games against Rangers. Break it down to goals per 90 minutes and Edouard has a remarkable record of 1.27 in the derby - his best return against any Premiership opponents aside from Motherwell.

Indeed, only the Fir Park club and Hearts have suffered more than Rangers at the hands of the Frenchman, with both conceding five times.

Continuation of combustible contests?

So far this season, Celtic average 1.17 yellow cards per league game. Rangers' average is slightly higher - 1.53 - but still relatively low. However, in the past three Old Firm games both sides have averaged the same number of yellow cards - 2.67.

Add Rangers' two sendings off in the three previous games to that tally and it is clear to see that the added tension translates to more cards.

Foderingham v McGregor

Rangers will be without Allan McGregor following his sending off against Hibs, but is there a significant drop off between him and Wes Foderingham?

This season, the former Scotland goalkeeper has saved an average of 74% of the shots he has faced - notably better than his understudy's average of 69% from last term. While a number of other factors play a part - such as the defenders in front of each custodian - such a drop off could explain why Foderingham conceded an average of 1.09 goals per game last season, while McGregor has only allowed 0.67 past him this time around.