Juventus coach Massimiliano Allegri is well aware having Cristiano Ronaldo gives his team an advantage in the Champions League, but he warned they are not obliged to win it simply because the Portugal great plays for them.

Ronaldo made the shock switch from Real Madrid to Juve in July having won the Champions League three times in a row.

The 34-year-old has shown no sign of letting up since departing LaLiga either, scoring 19 times in 24 Serie A matches, swiftly adapting to the rigours of Italian football.

For many, the signing of Ronaldo instantly made Juve favourites for the 2018-19 Champions League, particularly given they made it as far as the final in two of the past four seasons.

Allegri recognised Ronaldo's presence does give Juve a helping hand, but he also had a word of caution for the squad as they prepare to face Atletico Madrid at the Wanda Metropolitano in the first leg of their last-16 clash on Wednesday.

"It is not a question of obligation," Allegri told reporters in his pre-match news conference. "The Champions League is a goal.

"You need to play well and be lucky. Having Ronaldo is definitely an advantage, but it is the team that has to play important games.

"Ronaldo is the best in the world, and you have more chances to win it with him, but you do not win automatically."

Allegri is also mindful of the threat posed by Atletico, who themselves have reached two Champions League finals in five years, while he spoke highly of the job Diego Simeone has done at the club.

"The Champions League has always been a goal for Juventus, and it will be an important match [on Wednesday], as all the knockout stages played in the last few years have been," Allegri added.

"We have had high-level Champions League campaigns, but Atletico is an organised team and make their defensive platform their strength.

"I congratulate Simeone - he did, and is doing, an extraordinary job."