The prolific attacker is currently unavailable due to injury, but Messi's absence hasn't affected the Blaugrana's form so far, as players such as Neymar and Alexis Sanchez have stepped up to fill the void.
However, Busquest feels the Argentina international remains Barca's undisputed star player.
"Messi is as important to us as he was before," the midfielder told Cope. "He is the best in the world and he does amazing things. We miss him a lot."
Busquets then went on to discuss the potential arrival of Jose Reina as the club's new goalkeeper once Victor Valdes leaves the club at the end of the 2013-14 campaign.
"Reina is a great goalkeeper," the Spain international said. "It would be a good thing if he came to Barca."
The 31-year-old Reina started his professional career at Camp Nou, but left the club for Villarreal in 2002 before joining Liverpool three years later. He is currently on loan at Napoli until the end of the season.
Reina has a contract with the Reds until June 2016.