Musetti triumphed in a three-set classic to lift his first Tour-level trophy on clay in Hamburg last year, before Alcaraz won the US Open and rose to the top of the world rankings.
"I see (him as) a friend. He started a (new) way, a new generation," Musetti said after defeating Briton Cameron Norrie (27) in straight sets at Roland Garros on Friday.
"He won the first Grand Slam title after the big three, so he is an inspiration for us - for me, Holger (Rune), Jannik (Sinner), and whoever is behind him, and trying to push him and to get closer.
"The match in Hamburg gave me a lot of confidence... Of course, it's a completely different position, different status but I think we will enjoy our match."
Musetti, who reached the fourth round in Paris on his Grand Slam debut in 2021, has yet to drop a set at this year's Roland Garros and upset Novak Djokovic (36) in Monte Carlo in April.
Despite demolishing Canadian Denis Shapovalov (24) in three sets on Friday, Alcaraz said he was expecting a hard match against Musetti.
"It's a big challenge for me," the Spaniard said. "I remember the match in Hamburg. It was really, really tough. He's a really talented player.
"I know him very well. We played tournaments when we were kids... It's going to be a really fun match."
Alcaraz, bidding to win his first French Open title, is on course for a potential meeting with Stefanos Tsitsipas (24) in the quarter-finals and Djokovic in the semi-finals.
World number three Djokovic resumes his quest for a record 23rd major against Juan Pablo Varillas (27), who became the first Peruvian in 29 years to reach the fourth round at a Grand Slam.
Greek fifth seed Tsitsipas has quietly marched into the fourth round and will look to end the inspired run of Austrian qualifier Sebastian Ofner (27), who saw off Fabio Fognini (36) in five sets on Friday.
In the women's draw, second seed Aryna Sabalenka (25) and Sloane Stephens (30), the only Grand Slam champions remaining in their half of the draw, will clash on Court Philippe-Chatrier in the first women's night session of the tournament.
Ukraine's Elina Svitolina (28) will take on Russian ninth seed Daria Kasatkina (26) for a place in the quarter-finals after beating another Russian, Anna Blinkova (24), in the previous round.
Svitolina refused to shake hands with Blinkova out of respect for Ukrainian soldiers, following Moscow's invasion of her country last year. Sunday's opponent Kasatkina has left Russia and has been critical of the war.
"I'm thankful to Dasha (Kasatkina) for taking this position," Svitolina said. "That's what you expect from others, as well. It's really brave from her."
