Worried Kenny Miller says replacing Connor Goldson must be Rangers' top priority in the summer window.
And he also questioned Gio van Bronckhorst for taking Aaron Ramsey off against Celtic - feeling the Welshman could have got them back into the game.
Rangers ' defeat on Sunday leaves them six points behind Celtic and needing a minor miracle if they are to retain their title in the final six games of the season.
Longer term things also look up in the air with key man Goldson looking set to leave in the summer when his contract expires.
And former Ibrox striker Miller says finding a replacement for the centre-back, who has missed just three games so far this season, must be Van Bronckhorst's main priority.
He said on Go Radio: "If Connor Goldson leaves there's going to be a huge addition needed. He's been an ever-present, he's started pretty much every single game since he arrived at the club four years ago.
"He'll need to be replaced, that's the first one.
"I don't think Rangers have improved the starting lineup since last year. Aaron Ramsey definitely improves it if he's fit, we saw his class on Sunday and I was really disappointed he went off.
"He was (the one troubling Celtic). They had 42 or 43 crosses into the Celtic box, he's the midfielder that's breaking into the box. He wants to score goals, he's hungry to score goals, he's always been that way."
Fellow pundit John Hartson then raised it to Miller that John Lundstram has been a big signing after his summer move from Sheffield United.
Miller replied: "He doesn't get into the box though. That's the thing, Aaron Ramsey has always done it since he was a kid, he did it at Arsenal. He was even doing it for Juve and he's been doing it for Rangers.
"He did it at the weekend, with the chance that was offside. That ball from Lundstram should have been straight through to him and he would have been one on one.
"I was surprised to see him go off because Aaron Ramsey improves the starting lineup.
"But going back to the summer, I don't think any signings were made to improve that starting lineup.
"That will need to happen now and it's not just a reaction to potentially losing the league to Celtic.
"There may be bids in for other players that may leave, players who have been starters.
"But even if everyone stays, you have to improve. You can't just rest on your laurels, that's something we saw with Celtic two or three years ago when they allowed Rangers to get back into it.
"They had one foot on the neck and they let them up. Rangers have turned that tide under Steven Gerrard and it's important now that they improve in the summer."
