Cristiano Ronaldo joining Juventus cannot constitute a challenge, according to former Bianconeri striker Zlatan Ibrahimovic.

Ronaldo has hit 18 goals in 23 Serie A appearances for the Turin giants since signing from Real Madrid, topping the league's scoring charts.

Juve are 11 points clear of nearest rivals Napoli as they look to win Serie A title for the eighth year in a row, although they were dumped out of the Coppa Italia at the quarter-final stage by Atalanta.

Portugal international Ronaldo described joining Juventus as a "challenge" when he completed his move from Madrid in a deal worth €112million last July.

Ibrahimovic, who played for Juve between 2004 and 2006, previously took issue with Ronaldo's choice of words and he again criticised the prolific forward.

"I didn't say his transfer wasn't great," LA Galaxy star Ibrahimovic, 37, told DAZN.

"I said that it wasn't a challenge to join Juventus. It's not a challenge to go to one of the best teams in the world.

"Maybe it depends on what you mean by challenge. For me, a challenge is joining a team and taking them far. That's a challenge."

Juve are among the frontrunners for this year's Champions League, although they were given a testing draw against Atletico Madrid in the last 16.

Ronaldo's old club Madrid are hunting an unprecedented fourth consecutive title in the competition and Ibrahimovic is unwilling to predict the winner.

"This year is very open. There isn't a team who are better than all the others or a favourite," Ibrahimovic added.

"Maybe one of my old teams will win: PSG, Manchester United, Juve or Barcelona.

"Unfortunately Inter have been eliminated, while AC Milan aren't there. There are four teams and I hope one of them win it."