German international midfielder Sami Khedira believes Juventus face the biggest threat this season to their Serie A supremacy.
Juventus last year became the first team to win six consecutive Serie A titles and are just one point behind leaders Napoli midway through this campaign.
"This year is different from last year and two years ago. At the top of Serie A there are a lot of strong teams and all at the same level," the 30-year-old former Real Madrid player told Sky Sport Italia.
"Napoli but also Inter, Roma and Lazio, and of course Juventus. For this reason it will be even harder to win the Scudetto, we have to work harder than ever to try to take it home.
"I think it will be more complicated to repeat this season."
The Scudetto is not the only goal this season for the Turin giants as they resume the Champions League in February against English club Tottenham.
"There are surprises in the group stage, but the real tournament starts in the second round," he continued of the elite European title which Juventus have won twice in 1985 and 1996.
"There's Bayern Munich with their new coach, Manchester City or PSG, who havs great financial resources and quality players, there are also Real Madrid, Barcelona, Juventus, there are many teams that can win the Champions League".