Even Pep Guardiola would fail to close the gap on Celtic if he managed Rangers, former Hoops striker John Hartson has claimed.
But Hartson believes Steven Gerrard should take the Ibrox job because a "dire" Rangers team cannot get any worse.
The Liverpool youth coach is understood to be Rangers' top choice to take over now that Graeme Murty has left the club, but the size of the task was laid bare on Sunday when Celtic thrashed their rivals 5-0 to seal a seventh consecutive Premiership title.
The victory followed a 4-0 rout in their Scottish Cup semi-final, which culminated in Rangers suspending captain Lee Wallace and striker Kenny Miller following a dressing-room inquest.
Celtic have scored 30 goals against Rangers in two seasons under Brendan Rodgers and Hartson admits no manager could get close to the champions as things stand.
"Pep Guardiola couldn't do that," said Hartson. "Rangers are dire. They were embarrassing in the semi-final, their most senior players were embarrassing. Sunday, they were embarrassing.
"It's a mismatch at the minute. Rangers are in turmoil, on and off the pitch. They need serious investment. They need a lot of things. Celtic are flying on and off the pitch. They are a long, long way behind.
"Steven Gerrard will look at that and he'll say, if he takes Rangers, 'I can only go one way, and that's up'. They can't get any worse. And that's why I don't think it would do him any harm. He is going to a great club with huge backing, fans-wise."
Hartson believes Gerrard will have two major questions: how much financial help is available and how much scope does he have to clear out the "deadwood".
The former Wales striker added: "Their best player was out on Sunday, Declan John. They got him from Cardiff, initially on loan. And he wasn't even in the Cardiff team.
"He's been Rangers' best player this season. That's what you are working with. He has done very well, I know him from the national team, Wales."
The appointment of 37-year-old Gerrard would represent a major gamble for both parties.
"It's up to Steven whether he wants to wait another four years and work with the young players at Liverpool," Hartson said.
"Maybe he might get an opportunity to manage the Liverpool first team if Jurgen Klopp decides to go away.
"I see it as a wonderful opportunity. He can only take them up, he can't make them any worse.
"I think there will always be a place at Liverpool for Gerrard, so if he fails drastically like the last two managers, then I don't think it will damage him too much because Pep Guardiola couldn't improve Rangers at the minute. I don't think they have the quality."
Former Rangers striker Kris Boyd has echoed Hartson's comments, saying the Ibrox club are rudderless and with no plan.
He stated: "Six months ago you are trying to get Derek McInnes, tried and tested in Scotland, knows the game inside out, and six months later you are trying to get a youth coach.
"No disrespect to Steven Gerrard, but at this moment in time that's what he is. I don't think there is a clear direction or plan of where the club wants to go.
"I still don't know what (director of football) Mark Allen is doing. It would be interesting to see what's gone on with him.
"If you are the director of football and you try to bring in a manager who has been over the course and distance, knows exactly what is going on in Scotland, then all of a sudden you are going to Liverpool to take their youth coach, it doesn't add up.
"There needs to be a plan and direction and at this moment I don't think anybody knows."