Rangers caretaker manager Kenny McDowall admitted his first match in charge was "not good enough" after watching his team humbled by Hibernian.
Hibs eased to a 4-0 win and are now four points behind Rangers in the Scottish Championship, with leaders Hearts now 15 points clear.
"It was very disappointing to be two down after 12 minutes," said McDowall.
Hibs manager Alan Stubbs thought his team "dominated from start to finish" and were "outstanding".
McDowall was put in charge of the Rangers first team on Sunday after Ally McCoist, who had handed in his resignation and was working his 12-month notice period, was placed on gardening leave.
|Scottish Premiership play-offs explained|
|Scottish Premiership bottom team relegated, Scottish Championship winner promoted|
|Championship third- and fourth-placed teams play two-legged quarter-final|
|Winner plays Championship runner-up in two-legged semi-final|
|Winner of that plays Premiership second-bottom team in two-legged final|
However, the former St Mirren player could not prevent Rangers slipping to their fifth league defeat of the season at Easter Road.
"Our whole game plan went out the window [after Hibs' early goals]," McDowall explained.
"I don't know if a lack of commitment is the word I would use. They just did not look organised at times. They were not where they should have been on the park. Commitment? You should ask them.
"Were the boys mentally tired? I couldn't deny that was a part of it with the goings on and the situation. But do I want to make that an excuse? No.
"They are professional people. I will accept the responsibility for the result. I set the team up and the boys will accept responsibility for the performances.
"We will see where we go. We just have to keep trying to win games and see where that takes us. If it's a play-off it's a play-off. We're prepared to go there.
"At the moment I am just going to have to work with the squad that is there. I can't just invent players."
Rangers, Hibs and Queen of the South currently occupy the play-off spots and Alan Stubbs believes his side can overtake the Ibrox men.
"There's definitely a feeling there, we've got a lot of belief," the Easter Road manager told BBC Scotland.
"From the beginning to the end, it probably doesn't get much better than that.
"The way we played was outstanding, we've scored some brilliant goals. We dominated from start to finish and the players deserve a lot of credit for that."