Dominic Thiem has gone from Rafael Nadal's successor on clay to hardcourt champion: Filippo Volandri

Former World No. 25 Filippo Volandri believes that US Open champion Dominic Thiem has become a complete player over the past two years, and a serious threat to Rafael Nadal and Novak Djokovic's reign at the top of the world rankings.

After losing in the final of his first three Grand Slams (the 2018 French Open, the 2019 French Open and the 2020 Australian Open), Dominic Thiem won his first Major at the 2020 US Open. He also defeated both Nadal and Djokovic en route to the the summit clash of the Nitto ATP Finals in London.

Volandri, who is now the Technical Director at the Italian Tennis Federation, claimed that Thiem is no longer just a claycourt specialist, and that his success on hardcourts is proof of the progress he has made over the past two years.

"Dominic Thiem has become a complete player compared to two years ago, good to see from a technical point of view and now also from a stylistic point of view. Physically, he has made great strides, it was unimaginable until two years ago to see him win on hardcourt. The most common image of him was that of Nadal's successor on clay, then comes the success at the US Open and the two closing acts at the Finals," Volandri said.

Volandri also highlighted the improvements Dominic Thiem has made in his net game, and asserted that is the best player at the moment behind Nadal and Djokovic.

"Dominic Thiem has worked hard on his game, since last year he has started to go to the net a lot, if in 2019 he was often wrong, to date he has worked on those defects allowing him to be very solid even in that area. Medvedev was the best player of the ATP Finals, but behind Nadal and Djokovic at the moment there is first Thiem and then the Russian," Volandri added.

Dominic Thiem, Daniil Medvedev & others will challenge Rafael Nadal & Novak Djokovic in 2021 for Majors: Filippo Volandri

Novak Djokovic and Rafael Nadal

While Filippo Volandri expects Novak Djokovic to win more Grand Slams in 2021 and Rafael Nadal to continue his domination on clay, he thinks the field is much wider now with the likes of Thiem, Medvedev, Stefanos Tsitsipas and Alexander Zverev also being able to contend for Major titles.

"The generational change is already underway. In addition to the Big 3, there will be other names in the big tournament favorites roster. Novak Djokovic will win other Grand Slams, Rafael Nadal on clay can continue his domination, let's see Roger Federer next year," Volandri stated.

"But earlier if there were only the big favorites, now the others, like Dominic Thiem, Medvedev, Tsitsipas and Zverev, can really go all the way to a Grand Slam and win. There is room for them too," he continued.

Volandri also spoke about 19-year-old Italian tennis sensation Jannik Sinner, who he believes still needs some more time to mature before he takes the next big step.

"He's a 19-year-old boy. He has significant room for improvement. If you ask me if he plays the Masters next year, I tell you I hope so but it still seems early. We also give him time to grow, there are players who reach the top early but it takes years to take that further step forward," Volandri said.

"Take Dominic Thiem, two years ago he took home a Masters Series but he had to work for another two years to confirm himself as one of the best in the world," the 39-year-old concluded.