Celtic manager Neil Lennon says his players were "lazy" in the midweek defeat by Inverness Caledonian Thistle.
The Hoops crashed 3-2 to the Highlanders on Wednesday to hand the initiative in the title race to Rangers with three matches remaining.
Lennon knows that his team cannot afford to play as poorly against Kilmarnock on Sunday.
"The players know themselves, we have good players who made basic mistakes," said the manager.
Lennon felt that two of the three goals conceded to Caley Thistle were easily avoidable.
"The first goal was down to lazy defending," he said.
"The second goal you have to say was a good finish, but for the third goal again it was lazy defending which cost us."
Lennon rejected the notion that his side had lost their nerve as the championship finishing line looms large.
"It's not anything to do with nerves, it's people not doing their jobs properly," he commented.
"We have players that have won championships and promotions before."
The Northern Irishman hopes there will be more twists before the league is over but says his team must make no mistakes from here on in.
"We have to force Rangers to win their games," he said.
"Every time we've had a bad result this season, we've bounced back.
"We must win at Kilmarnock."
Celtic forward Shaun Maloney says the players were suffering after the shock defeat to Terry Butcher's men.
"Yesterday, we were very low, but today we move on to Kilmarnock," he said before recalling the the 0-0 draw with Rangers on 24 April.
"After the result at Ibrox, the positive thing was that it was in our hands. Now we've lost that with the defeat at Inverness.
"We need to make it as difficult as possible for Rangers to win the league. It would be devastating if we didn't win it."
Maloney also conceded that speculation about Lennon's future will intensify should he fail to deliver the league championship.
"Questions are asked every year at Celtic if we don't win the league", he added.