Rangers first team coach Michael Beale has indicated that tiredness and mental fatigue played their part in the Gers' Old Firm defeat against Celtic before the last international break.
Hopes were high amongst Steven Gerrard's men that they would compete well with Celtic when they headed to Parkhead before September's international break.
But Celtic enjoyed much the better of the derby clash and ran out 1-0 winners, putting a dent in the progress Rangers had made under Gerrard.
Rangers were in action in Russia in the Europa League on the Thursday before their Sunday meeting with Celtic and Beale says when the Gers headed to Parkhead they were just about ready to burst.
"The pre-season period in Spain was hugely important for that [fitness] and we're lucky we never wasted a day there", Beale said on Rangers TV.
"If you look at the group that came with us and the group now, it is completely different, with about a turnover of ten or twelve players from then.
"So you're trying to get those players up to [speed with] the ideas and it's not easy when you're doing that via a powerpoint presentation or a tactic board – you actually want to go through it with them on the field.
"But we've had to be very, very careful of energy levels.
"And I just think before the international break it maybe just caught up with us.
"I think we'd had two or three games when we'd gone down to ten men quite early in the games", the first team coach stressed.
"That adds an extra weight on the players and also I think mentally it's been quite tough with the players and the high pressure games.
"So I felt before the international break we were almost ready to burst."
Rangers got back on track after the international break with a 4-0 thrashing of Dundee and have continued to impress in the Europa League, with their latest result a 3-1 win over Rapid Vienna.
