Goalkeeper Edwin van der Sar wants Manchester United to regain their focus on Wednesday when they face Celtic at Parkhead in the Champions League.
The Holland international was angry and disappointed at the way the Premier League and European champions almost let newly-promoted Hull off the hook at home.
United were 4-1 up and cruising but then conceded two late goals before clinching a narrow nail-biting victory.
Van der Sar believes there must be no repeat in Glasgow or they could suffer the consequences in front of a partisan crowd.
"We got a warning on Saturday," he told MUTV. "We have to make sure we finish teams off.
"We must not stop halfway through the second half and start thinking about the next game.
"You have to take it one game at a time, win it with confidence and then move on."
United are looking to complete the double over Celtic after beating them 3-0 at Old Trafford last month.
Van der Sar is keen to chalk up another clean sheet following his experience against Hull.
He said: "For a goalkeeper and the players you do not like to concede three goals.
"Of course you want to win games but by 1-0, 2-0, 3-0. When you are 4-1 up, you do not expect the other side to score another two goals. But Hull are a team that never give up."
A victory for United against Gordon Strachan's side would give them 10 points and almost certainly a place in the first knockout stage.
That was manager Alex Ferguson's initial target when the draw was made in Monaco. However he faces a midweek selection dilemma as United also face Arsenal in a crucial league match at the Emirates Stadium on Saturday lunchtime.
