Goals from Steven Davis and Nacho Novo kept Rangers at the summit of the Clydesdale Bank Premier League despite a late strike from David Clarkson which proved to be too little too late from the visiting side.
“I feel it’s the worst performance we’ve had since I’ve been at the football club,” said McGhee.
“We were inept in every department, we were second to every ball, we never won a header, we never kept a ball. I’ve never felt as disappointed as I do today about a performance since I’ve been at the club.
“I was up at 7am this morning talking to Scott Leitch [assistant manager] on the phone and I thought we were coming here to win, I really did. I felt we had a team set up with strength, energy, ability. We love coming here and it just all seemed right to me — but we never turned up.
“The fact that we didn’t lose 5-0, you would need to ask Walter [Smith] about that. Because if a team had played against me like that, I would have been expecting to win 5-0.”
The Motherwell boss refused to use their UEFA Cup exploits against French side Nancy on Thursday night as an excuse for the lacklustre display.
“It was not even 1% of anything to do with Thursday night,” he said.
“I expected to do well here today. I thought I set my team up well but at half-time, at 0-0, we still hadn’t started. I still felt at half-time, if they found the proper gear that I know they’re capable of, then there was something here for us today, that we could win the game. But we never found it.”
Smith took the bold decision to drop regular first choice goalkeeper Allan McGregor in favour of Neil Alexander and the Rangers boss warned that no-one’s place in the team is guaranteed.
“We’ve got a big pool of players and I have to show everyone that they have to be at the top of their game,” he said.
“Neil came after Allan McGregor had an exceptional season for us until getting injured in the latter stages of last season and he played very well.
“As soon as Allan came back, he came back into the team and I just feel at times that I have to use the whole of pool of players to keep an edge in the squad. We don’t have the number of games that we had last season and it’s up to every player to make sure that he keeps himself as well-prepared as he possibly can.
“It will happen to more players than Allan McGregor throughout the season. We have a squad of players and we have to use them.
“As long as it keeps everyone at the proper level, that’s fine.”
Alexander, Broadfoot, Bougherra, Weir, Dailly, Davis, Pedro Mendes, Thomson, Beasley (Novo 72), Boyd, Miller.
Graeme Smith, Quinn, Craigan, Reynolds, Hammell, Hughes (Darren Smith 67), Malcolm, Lasley, Clarkson, Porter, Sutton (Murphy 54).
E Smith (Scotland).