Rangers gave the Old Firm Derby away to Celtic, but Giovanni van Bronckhorst does not think it will be decisive in the Scottish Premiership title race.
Celtic took the lead through Reo Hatate inside five minutes at an electric Parkhead on Wednesday and completely controlled the clash between the top two during the opening period.
Hatate rifled in a brilliant second and two minutes later crossed for Liel Abada to make it 3-0 on the stroke of half-time.
Rangers improved after the restart but were unable to stop their 21-game unbeaten run coming to an end, with Celtic replacing them at the Premiership summit and going a point clear.
"It seemed like it was the first Old Firm game we'd played. We know what the Old Firm will bring, what we have to do … but it seemed like we weren't ready for it," Van Bronckhorst told Sky Sports.
"You see the way we gave the goals away. It's the sharpness, I cannot say otherwise. It's not going with your man, not being ready for the battles. I think it was unbelievable the first half I saw.
"I think our Old Firm game started in the second half. We were much better, much more aggressive and we played the second half really well. But in the first half we gave the game away.
"It wasn't something I expected. When I see the trainings we had, the focus we had before the game, but when the whistle blew, we were just waiting for the goal to be scored. We were too naive and we deserved to be down 3-0 with the way we played.
"We had an honest conversation in the locker room after the game.
"We're not the first Rangers team to lose. I lost very big here as a player, but we eventually became champions that year. Of course, we wanted to win this game, but these games don't decide the championship. We still have many games to play and we have to be ready."
The victory was Ange Postecoglou's first since taking charge of Celtic and ended a six-game winless run against Rangers in the league.
The Australian was thoroughly impressed with how his team outplayed Rangers and believes there is still plenty more to come from the Bhoys.
"Our first 45 minutes were outstanding; three great goals," Postecoglou told the BBC.
"Our football was pretty special and their keeper pulled off some great saves. In the second half, we had to defend a bit more but we've been a team that can do that. It shows another layer. We knew the consequences, what it meant to our supporters, and we stood up.
"Considering the context of the game and the opposition, I thought our football was outstanding. It's the kind of football team we want to be. It doesn't mean you disrespect or dismiss the opposition. We are still developing, but we want to take it to the opposition, and if we do that, we can take it to any opposition.
"We've still got key players missing, very influential players. Some are just in the door. Reo Hatate and Matt O'Riley have played fewer than five games. Our target was not top spot, our target is to win things, and if we're going to win things, we have to keep improving."