Despite offering the 34-year-old the chance to stay on for another season, Busquets has decided to call time on his Blaugrana career when his deal expires at the end of the month.
The Spaniard's departure will bring the curtain down on a glittering 15-year spell in Barca's first team, during which he has won three Champions League crowns and nine La Liga titles in Catalonian colours.
With Busquets still a fundamental part of Xavi's plans during his farewell season, Barca are searching high and low for adequate replacements and have been strongly linked with a move for Zubimendi.
The 24-year-old is already a Copa del Rey winner with his boyhood club and played a major role in helping Sociedad qualify for the 2023-24 Champions League with a fourth-placed finish in La Liga this season.
Zubimendi ended the 2022-23 season with one goal and four assists from 44 games in all tournaments, taking his total for Sociedad to four goals and six assists from 143 appearances in total.
Back in October, Zubimendi committed his future to Sociedad with a new long-term contract until 2027, and the Spain international also snubbed interest from Arsenal in January to continue working under Imanol Alguacil.
Since then, Zubimendi has continued to play down talk of an exit from his current club, despite being branded an "extraordinary pivot" by Xavi, and the 24-year-old has seemingly laid any speculation to rest.
Zubimendi has been under the wing of 33-year-old Asier Illarramendi at Sociedad, but the current White and Blues captain will leave on a free transfer this summer, and Zubimendi has stated that following in his senior's footsteps means more to him than succeeding Busquets at Barcelona.
Speaking to El Diario Vasco after arriving for Spain duty this month, Zubimendi said: "Inheriting Asier Illarramendi's '4' motivates me more than Sergio Busquets' '5'."
Zubimendi's comments come as another blow to Barcelona in their search for a new defensive midfielder, but the Spanish champions are thought to possess a list of alternative options.
A swap deal involving Ansu Fati and Wolverhampton Wanderers' Ruben Neves has been mooted, but the move is now in jeopardy after agent Jorge Mendes affirmed that the former wants to stay at Camp Nou.
Xavi has confirmed that Barca are looking at Bayern Munich midfielder Joshua Kimmich, but the Bundesliga champions are expected to resist offers for the Germany international this summer.
Fiorentina and Morocco lynchpin Sofyan Amrabat could be a more attainable target, and Barcelona are believed to have failed with a loan offer for the 26-year-old in January.
However, Amrabat's brother and agent Nordin Amrabat has now claimed that Fiorentina could be open to selling the World Cup semi-finalist this summer.