Gianfranco Zola expects next month's clash between Napoli and Juventus to prove decisive in the race for the Scudetto.
Napoli saw their lead at the top of Serie A reduced to just one point on Saturday when they lost 4-2 at home to Roma, Juve having beaten Lazio 1-0 away earlier in the day.
Zola was a member of the Partenopei squad that last won the domestic title in 1989-90, and he had considered Maurizio Sarri's side favourites to emulate that feat this term.
The 51-year-old is now pinpointing the meeting of the top two at Allianz Stadium in Turin on April 22 as an all-important showdown.
Speaking to Omnisport, he was asked which team is most likely to be crowned champions: "One week ago, I would have said Napoli, 100 per cent.
"Now, I think it's tough for them, but it's still very open. Everything will be decided in Turin.
"Napoli suffered a tough blow when they lost at home to Roma, but they have the skills to win the league. Their squad deserves such an achievement, because they play very, very well.
"I believe in this Napoli side, but at the same time, I think Juve are a formidable club with endless resources. It won't be over until the end, but I do believe Napoli have a great chance."
Another of Zola's former clubs, Chelsea, won the Premier League last season but have struggled to reach the same level in 2017-18.
Antonio Conte's side are fifth in the table and, with nine games remaining, face a battle to qualify for the Champions League.
"Well, it hasn't been the best Chelsea, to be honest, especially the game against Manchester City, it wasn't a high standard game," he said of a dour 1-0 loss at Etihad Stadium.
"But to be fair, the last time I saw them play against Barcelona they really played well and they deserve more than they had," he added, referring to the 1-1 draw at home in the first leg of the Champions League's round of 16.
"So I think it's certainly a crucial moment for the team and hopefully in the next couple of games they are going to get good results."
Asked if the Blues are capable of finishing in the top four, Zola said: "I believe so. Chelsea is a good team, they have good players. So, it's still open and there is a little bit of a gap but I think they can still do that."
Gianfranco Zola was speaking at the Geneva International Motor Show, on behalf of Yokohama Tyres, the principal partner of Chelsea Football Club. For more information, visit: http://www.yokohama-online.com