McLeish, who won the treble with Rangers, told BBC Scotland that he felt there was a ‘lack of stamina’ in Pedro Caixinha’s side as they attempted to find a way back into the Old Firm clash.
The ex-Scotland manager told the BBC: “When the second goal went in, I felt Rangers didn’t have the legs of Celtic.
“it hit the mentality big time in the fact that they lost a goal, but I felt there was a lack of stamina in trying to match Celtic after that, because Celtic seemed to get much more space after the goal.
“When you lose a goal, mentality is one thing but when [the players] don’t look fit enough that’s another.”
McLeish’s comments echo those made by Michael O’Halloran, the Rangers forward currently on loan at St Johnstone, earlier this month.
O’Halloran described Caixinha’s training methods as ‘different’, claiming that he needed to do extra in order to keep himself fit.
He said: “I felt I was needing to do a lot of extra training to keep myself fit. I maybe wasn’t getting a lot out of the sessions, they weren’t very demanding to be honest.
“I felt I was having to go and do extra myself. I wasn’t playing at the time, but I felt I had to do extra to keep myself ticking over. I certainly didn’t keep myself fit through the training.”