Nineteen-year-old ATP sensation Joao Fonseca has lauded Carlos Alcaraz. The Brazilian, who is widely seen as a player with the potential to become one of Alcaraz's fiercest rivals in the years to come, touched on the Spaniard's importance in present-day tennis. Fonseca also spoke up about the positive impact that observing the reigning World No. 1 has had on him.Set to lock horns with Alcaraz for the first time on Monday, December 8, at the Miami Invitational exhibition event, the Brazilian cast his mind back to training with the six-time Major winner at this year's Wimbledon Championships and how significant it was for him."He’s so important to our sport, and just being there (they trained together at the last Wimbledon), experiencing that moment with him, meant a lot to me," Fonseca told SporTV. (translated from Portuguese)Joao Fonseca went on to state the confidence boost he got after Carlos Alcaraz recently laid bare his admiration for what the Brazilian brings to the tennis court."Watching his training, seeing how he prepares for matches, it’s been invaluable for my own development. And recently receiving a compliment from him, as you mentioned, is something really important that helps me keep going and maintain my confidence," he added.Despite voicing high praise for Joao Fonseca, Carlos Alcaraz delivered his verdict on where Brazilian can improveJoao Fonseca at the 2025 Swiss Indoors Basel (Source: Getty)Joao Fonseca, in his admission about Carlos Alcaraz, was referring to the following compliment that came his way from the Spaniard."He's a special and incredible player. The power he has is impressive, his serve is very good, something that, for me, when I entered the circuit, was what I struggled with the most. João also has a brutal forehand," Alcaraz said. (as reported by O Globo)However, the reigning World No. 1 also highlighted an area of improvement for Fonseca, adding:"If I had to point out something to improve, it would be his mobility."The Brazilian's 2025 tennis season turned out to be a memorable one. Having started the year as the World No. 145, his performances and results throughout the year helped him finish it as the 24th-ranked men's singles player in the world. He also captured his maiden ATP Tour-level title this year at the Argentina Open and later, was crowned the new champion at the more prestigious Swiss Indoors Basel.Meanwhile, Carlos Alcaraz ended 2025 as the year-end No. 1, having won eight titles throughout the season, including the French Open and the US Open.