Celtic dropped more points last weekend when they played out a 1-1 draw against St. Johnstone at Parkhead on Sunday.
On the same day, Rangers hammered Ross County 4-0 away from home and extended their lead at the top to 13 points, while playing two games fewer than the current champions.
McManus thinks Rangers look in such superb form and Celtic in such poor touch that Steven Gerrard’s men could end up winning the title by 20 points.
He believes the Bhoys must look over their shoulder as there is more chance of other teams replacing them in second than of Neil Lennon’s men catching up with Rangers in the title race.
McManus said on PLZ Soccer: “To be honest, the way Celtic are playing at the minute there is more chance of Aberdeen or Hibs catching up to them for second place than them catching Rangers up for first place.
“There is absolutely no chance of Celtic catching Rangers.
“In this form, Rangers will win the league by 20 points.
“Something has got to give.”
Rangers have conceded just three goals in the Scottish Premiership so far, while Celtic have leaked 14 goals.
