Former Rangers striker Derek Johnstone says there is a "massive gap" between Mark Warburton's side and Celtic following their Old Firm defeat on Saturday.
The Gers endured a torrid afternoon at Celtic Park as they went down 5-1 to Brendan Rodgers' side and had new signing Philippe Senderos sent off on his debut.
That red card left Rangers even more exposed as they tried to get back into the game at 3-1 but Johnstone says his former side have defensive frailties which were on display throughout the match and which must be addressed.
"Looking at it yesterday, there is a massive gap," Johnstone told Sky Sports News HQ.
"I think Rangers proved early on they could match Celtic without having any penetration up front but then something goes in the mind and they make mistakes and they are punished for it.
"They are going to have to eradicate all these mistakes, they are going to have to work very hard so it is not good for the manager but what he is going to have to do is work hard.
"What he has got, the players he has got now, is what he has to work with because he can't do anything until January if he is going to bring somebody else in. They are just going to have to work harder, certainly on the defensive side of their game, they are going to have to work harder."