"Thinking I won Wimbledon is tough to believe. I can't believe that I won and beat Novak (Djokovic), probably it will take some days to believe," Alcaraz told journalists.
On Sunday, Alcaraz beat Djokovic in five sets to win the second Grand Slam title of his career.
"Since Wimbledon, I didn't touch the racquet, today will be the first time," said Alcaraz, who takes on 111th-ranked Belgian David Goffin later on Friday.
"I'm a little bit tired, I'm not going to lie," he said.
"I had some days off to rest a little bit. I'm feeling great right now. I'm here to make people happy watching the match."
The world number one battled past seven-time Wimbledon champion Djokovic after a defeat to the Serb in the French Open semi-finals during which he suffered cramp.
But Alcaraz believes that he was "not well prepared mentally" before the Paris claycourt tournament.
"I couldn't deal with the pressure that Novak put on. I relaxed, doing some mental exercise before the match that probably I didn't do in Roland Garros, that helped me a lot."
In Nice, Alcaraz teams up with 72nd-ranked Rebeka Masarova, against the Belgium pairing of Goffin and Elise Mertens.
"We're not used to playing with women, mixed doubles. I wanted to have this experience," he continued.
"It feels great. I'm really happy and excited to be here."
After the Hopman Cup, Alcaraz will compete in the Masters 1000 in Toronto from August 7th and Cincinnati from August 13th.
"Right now, my focus is on Toronto, which is a Masters 1000 and really important, and Cincinnati, but, of course, the main goal is the US Open," he added of the final Grand Slam of the year which begins on August 21st and where he will defend his title.
