Walter Smith insists his players have to remain focused to have a chance of winning the domestic treble this season.
The Rangers boss watched his side squander a two-goal lead in Sunday's 3-3 draw with Dundee United in the Active Nation Scottish Cup quarter-final.
Smith, whose team are 13 points clear of Celtic at the top of the Clydesdale Bank Premier League and face St Mirren in Sunday's Co-operative Insurance Cup final at Hampden, warned: "What happened against United is something that worries me, for the simple reason that everyone is saying we're on for a treble, and that is premature."
He added: "It's the first time I've seen my team relax in that manner and allow the opposition to come back.
"Once we scored the third goal there was a slackness that came into our play. That slackness is unusual for our boys. They've been fantastic in their approach.
"I think a bit of complacency could come in because the expectation is that, with this points gap in the championship, people say you've won the league.
"So this sends out a message to everybody that we won't achieve unless we remain fully focused on what we have to do.
"We have a cup final to play on Sunday. But we have a whole load of cup finals to play if we are going to succeed this season.
"I know everyone is saying I'm just playing at it when I say that, but this shows that it's not the case. I'm making a realistic appraisal of what we have to do between now and the end of the season if we are going to succeed.
"We now find ourselves in a really tough replay at Tannadice, and we might still have to go there twice in the championship."
Copyright (c) PA Sport 2009, All Rights Reserved.
Do YOU want to write for GiveMeSport? Get started today by signing-up and submitting an article HERE: https://www.givemesport.com/writeforgms