Ally McCoist says both Alfredo Morelos and Odsonne Edouard are invaluable for the Old Firm but insists Rangers cannot afford to sell their Colombian striker in January, no matter the price.
Morelos has scored 28 goals so far this season and has proven almost indispensable both in the Scottish Premiership and in Europe as Rangers qualified for the last 32 of the Europa League while Edouard showed his importance to his side after coming off the bench to play a key role as Celtic won the League Cup final earlier this month.
Celtic are five points clear at the top of the Scottish Premiership going into Sunday's Old Firm meeting, live on Sky Sports, where Morelos will once again set out to break his duck in the fixture after a frustrating afternoon at Hampden three weeks ago.
But McCoist insists his former side cannot easily replace Morelos' goals if he were to be sold in January and says supporters see a first league title since 2011 as more important than a huge transfer fee.
McCoist told Sky Sports News: "They are vital to both teams. Looking at the squads I think 'reliant' is not the right word, but Rangers really need Morelos' performances and goals. Celtic need Edouard's performances.
"I think they have got more goals round about them and maybe more potential match-winners in (James) Forrest, (Ryan) Christie and (Callum) McGregor and lads like that. Whereas I think Rangers have been enjoying the success of Morelos playing very, very well. Both players are vital for their teams but probably more so Morelos for me."
He added: "It wouldn't guarantee the title [if one was to leave in January] but it would guarantee discontent among supporters!
"I heard Steven (Gerrard) say there is no way Morelos would be leaving in the January window and I think every Rangers supporter hopes and prays that that is the case and I don't think for a minute Celtic fans would want to see Edouard leave in the January window. It is too important for both clubs.
"That said, we all understand the importance of finances in top-level sport these days, particularly Scottish football and if it makes fantastic business sense then I can understand the business guys making that decision but that's not what the supporters want to hear.
"The argument is that you can't put a price on that first league title in years. The vast majority of supporters, myself included, would tell you that they don't care what the fee is - you cannot put a price on that first league title for Rangers and Steven Gerrard since they have come back from where they've been. I understand the business and financial side of it in terms of running a club but, for me, you can't put a price on it."
'Rangers need consistency after winter break'
Elsewhere, McCoist insists Rangers must continue to show consistency if they are to maintain a challenge to Celtic after dropping off the pace after New Year last time out.
Rangers ended last year with a 1-0 victory over Celtic at Ibrox to ensure they went into the winter shutdown level on points with their Glasgow rivals at the top of the table but they were unable to keep pace when the action resumed and McCoist says that cannot happen again.
"Consistency [needs to change for Rangers]. Rangers went into that winter break on the back of a victory against Celtic and then didn't start again with the same momentum Celtic did after the break," he said. "Celtic kicked off and put the afterburners on and it looked early on after the break that they were going to win the league which they obviously did.
"Rangers have to show the same level of consistency that they have shown in the first part of the season. They just have to attempt to put Celtic under the kind of pressure that they haven't been under in the last three or four years and perhaps ask them questions that they haven't been asked.
"It [consistency] has been addressed up to a point but the medals aren't handed out at this moment in time. If both teams are level or round about each other in February or March, that's when the pressure really kicks in and questions need answered."