"We thought about winning the game now we need to think about what happened with some players, what happened with some set-plays," the Brazilian tactician told Sky Sports.
"We need to change something in the future."
The former Brazil coach is convinced that United's opener was the turning point in Sunday's match.
"We didn't have many good chances and in the last minute of the first half we conceded a goal that changed everything," said Scolari.
"In the second half they played more freely and we gave them space which they like because we had to go for it."
"We didn't come here to play for this situation."
Despite the defeat, Chelsea are still second in the Premiership with 42 points, one ahead of third-placed United, who have two games in hand.