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 when Graeme Murty's short-term contract expires in the summer, but the size of the task was laid bare on Sunday when Celtic thrashed their rivals 5-0 to seal a seventh consecutive Ladbrokes Premiership title.
The victory followed a 4-0 rout in the William Hill Scottish Cup semi-finals which culminated in Rangers suspending club 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, experienced or otherwise, could get close to the champions as things stand.
"Pep Guardiola couldn't do that," said Hartson after attending the PFA Scotland awards.
"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 if he took the job 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" from the Ibrox squad.
The former Wales striker added: "Their best player was out on Sunday, Declan John, and they got him from Cardiff, initially on loan. And he wasn't even in the Cardiff City 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."
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