The pair were tied on five titles each until Messi won the 2019 award back in December. Ronaldo finished third:
The Portuguese forward has started the new year in brilliant form, scoring four goals in two appearances, including his first hat-trick for Juve in Serie A:
Sarri, who took over as Old Lady boss in the summer, wants to help Ronaldo join Messi on six Ballons d'Or, per Sacha Pisani of Goal:
"I would like to help Cristiano win the sixth Ballon d'Or first. It's really annoying thinking that someone won more [Ballons d'Or] than him. I think about him, and I think helping him, it is my goal and the goal of the team. It is right for him."
That will be his and Sarri's aim this term, as well as winning a ninth consecutive Serie A title for Juve.
Despite being one of Europe's biggest clubs, the Old Lady have a relatively poor record in the Champions League.
They have won the famous trophy twice, but their last triumph was in 1996.
Since then, Juve have lost five finals in Europe's most prestigious tournament to take their tally of runners-up places to a record seven.
One of the key reasons Ronaldo, 34, was signed for £100 million from Real in July 2018 was to help the Old Lady finally go all the way in the Champions League.
After topping Group D in the 2019-20 tournament, Juve have drawn Lyon in the last 16, an eminently winnable tie for a side of their quality:
If Ronaldo can continue his current goalscoring form and help Juve to win the Champions League, and edge out Inter Milan in a tight title race, he will be in the running for a sixth Ballon d'Or gong come the end of 2020.