The 34-year-old joined Barcelona's academy system in 2005, initially representing the club's B team before making his first-team debut in 2008.
The midfielder has featured on 690 occasions for the Catalan giants, contributing 18 goals and 43 assists in the process, while he has won nine La Liga titles and three Champions League trophies.
Busquets's current deal will expire next June, though, and there has been a host of speculation surrounding his future at the club.
The Spain international has been strongly linked with a switch to the MLS, and a number of North American clubs are believed to be showing an interest in his services.
Xavi has said that it will be Busquets's decision whether he signs a new deal, and the club's head coach also defended the experienced midfielder amid recent criticism.
Busquets has remained a key player for the club this term, but he has been substituted early in the team's last two games against Inter Milan and Real Madrid.
"When we lose everyone gets criticised, Busquets is still an important player for us, he's the captain and he always helps us, Busquets and all the captains, we have a great dressing room," Xavi told reporters.
"Busquets' contract expires, yes... but we are still in October. He will decide. I took it as the season progressed. I had a renewal offer but decided to leave.
"Busi doesn't have a clear replacement, [Miralem] Pjanic and Nico [Gonzalez] wanted to leave... but now we have options like Frenkie [de Jong], [Franck] Kessie, or even the option to use a defender there. Busquets is still an important player for us."
Xavi also suggested during his press conference ahead of the Villarreal clash that Ansu Fati could be in line for a start against the Yellow Submarine.
"He's (Fati) very good. The other day he went very well, he participated in the goal and had the chance to equalise. He'll participate for sure. He's going to be important," said the head coach.
"We will see tomorrow if there is any change (in the wide areas). The rivals are giving us a lot of coverage. We have to circulate the ball faster so that the wingers receive equal numbers."
Raphinha, Robert Lewandowski and Ousmane Dembele have been Xavi's preferred front three this season, but the former found it difficult to make his mark against Real Madrid last time out.
Fati, 19, has scored twice and registered three assists in 13 appearances for Barcelona this season, although he has not found the back of the net in La Liga since September 10.