Nadal tips teenagers Alcaraz, Sinner as future champions
Alcaraz has been making waves since his ATP Tour debut last year and burnished his credentials by upsetting top seed David Goffin in the Great Ocean Road Open last week.
He swept past fellow qualifier Botic Van de Zandschulp 6-1, 6-4, 6-4 in the Australian Open first round and 20-time Grand Slam winner Nadal has high hopes for him.
"He has all the ingredients to become a great champion. It's all about how much you are able to improve during the next couple of years."
Alcaraz was barely inside the top 500 at the start of last season, but has raced to 141 and is charging towards the top 100.
World number two Nadal also had high praise for fast-improving 19-year-old Italian Jannik Sinner, who in November became the youngest ATP champion in 12 years when he won in Sofia.
Sinner, ranked 32, backed up his breakthrough by clinching the Great Ocean Road title and was unlucky to crash Monday over five tough sets to world number 11 Denis Shapovalov.
"Honestly, he's a great guy, he's humble, he's relaxed, he's a good worker," Nadal said of Sinner, who he also practised with in Australia.
"The same thing that I talk about Alcaraz -- he's already there fighting for important things, winning a title just the previous week.
"I mean, I am sure he's going to finish this year in a high position of the ranking. I don't have a doubt of that."