Cristiano Ronaldo says Real Madrid cannot take their Champions League semi-final lead over Atletico Madrid for granted – although he accepts it is "a very good" advantage.
The 32-year-old scored a hat-trick for the second European match in a row to give the holders a 3-0 first-leg victory at the Santiago Bernabeu and take a big step towards the final in Cardiff.
Ronaldo, who is now on 399 goals for Madrid in all competitions, was delighted with his side's overall display, but has urged his team-mates to stay focused for the match at the Vicente Calderon.
"For me all games are important, it depends how you want to interpret them," he told UEFA.com. "I always look at them in a serious manner because I want to win and goals allow us to relax and have an advantage.
"It's an advantage and I won't lie – a good, very good one. But we can't take anything for granted. We have to go into the return leg at the Calderon fully focused.
"We know football is a box of surprises and for that we need to be wary. We know it will be a difficult game, but we've got a good advantage. We need to be wary and go there and play a good game, too.
"The side were tremendous as a whole. We played well from the first to the last whistle. Fortunately, the chances went in.
"The three goals give us an advantage, but the tie is not over and you cannot joke around with football. Atletico Madrid are a great team and they're in the semi-finals for a reason."
Ronaldo had earlier again called for Madrid fans to stop whistling him at the Bernabeu, with a small number of fans having targeted the Portugal captain much like they did during the 4-2 quarter-final second-leg win over Bayern Munich.
Club captain Sergio Ramos described the supporters' reaction as something of a wake-up call for the players, but stressed that Ronaldo's commitment should never be questioned.
"We'll all remember that he's a unique player and a legend of our club," said Ramos. "It's impossible to please everyone. When they boo you, it's a little warning sign.
"But above all, they have to have that margin of error with the players because you have to go back home empty after having given everything and, in that sense, Cristiano cannot be blamed for anything. Quite the opposite, actually."