Real Madrid goalkeeper Thibaut Courtois says Celtic pushed them all the way on Tuesday night.
The title holders began their Champions League defence with a 3-0 win in Glasgow.
Courtois said, "The first half was tough going, they made a very strong start and there was an amazing atmosphere inside here. Within the first couple of minutes, they'd already had two corners, a shot that Militão or the post got in the way of to save us.
"We then began to find our tempo and worked out how best to handle them and we improved as the minutes ticked by. We dominated things in the second half. It was a deserved win. Had they scored early on, it would have been more of a struggle for us.
“We have a lot of players within the squad and are in good shape fitness-wise. We had to get used to their high-tempo football. The ball went out of play and there was immediately another ball in play and even on the corners, they got the game moving very quickly so that we hardly had the chance to catch our breath. They played better in the first half, but Vini Jr. had a good chance. We were better after the break. Rüdiger and Eden, who provided an assist and got a goal, played an important part for us tonight.
“When I played here with Atlético in the Europa League, the atmosphere was unbelievable. It's a stadium I love coming to. On Matchday 1 of the Champions League, it's been a fantastic atmosphere, always positive and getting behind their team. They applauded us as well. That's the beauty of football. It's a pleasure to have played here and to be coming away with the win."
On goalscorer Eden Hazard, Courtois also said: “It was important for him to feel right. He was downhearted after the penalty miss against Celta and then he missed the last couple of LaLiga games. He's a wonderful player, he's got so much quality. The first five minutes were tough but once he got up to speed with the game he played a key role for us. The goal and the assist show what he's all about. He'll be pleased, he's shown the coach he can take more opportunities."
