Newcastle United were given a "wake-up call" as they slipped to the bottom of the Premier League after a 2-0 loss at West Ham, said boss Steve McClaren.
Ex-England coach McClaren, 54, took over in the summer but remains without a Premier League win after two Dimitri Payet goals gave the Hammers victory.
"I'm very disappointed and this is a big lesson," said McClaren.
"These games hurt like mad, but you need them to get the message across and we need a reaction on Saturday."
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Payet gave the Hammers an early lead when he curled the ball past Tim Krul from the edge of the penalty area.
The Frenchman scored his second three minutes after half-time with a rebound after Victor Moses hit the crossbar.
Newcastle's team coach was stuck in traffic in east London before kick-off and the players had to walk the last mile to the ground.
McClaren refused to blame his side's poor performance on the disruption.
"The preparation was short, but we had to deal with that and we didn't," he said. "I don't want to make any excuses.
"West Ham came out flying and scored within 10 minutes and in the second half we huffed and puffed without that quality in the final third.
"This is a journey and it has been two steps forward one step back so far, but this was two or three steps back. Our final ball was poor."
The Magpies, who have two points from five matches, host Watford on Saturday (15:00 BST kick-off).
West Ham boss Slaven Bilic praised the impact of Payet, who has scored three times since a £10.7m move from Marseille in the summer.
"Payet is a player I wanted from the start," said Bilic. "He is not only a great player but he makes players around him better.
"We fully deserved the three points, we were better from the start and we scored at the right time."
Victory took the Hammers into fifth place, six points behind leaders Manchester City.