The Spanish midfielder believes that the Malian was a key member of the team, and insists that he wanted to play for Spain at the Olympic Games in London
The Malian midfielder joined Chinese Super League side Dalian Aerbin earlier in the summer after becoming disillusioned with life at Camp Nou as he often had to settle for a place on the bench.
Earlier on Thursday, Keita lamented that he did not play more often under Barca coach Pep Guardiola, and Busquets thinks that the 32-year-old's absence will leave a gap in his team.
"With Keita gone, we lose a lot, both on and off the pitch." Busquets explained at a press conference.
"He is a great player, very strong and physical, and a great person, and everyone liked him in the dressing room."
Busquets then commented on Spain's surprising early exit at the Olympic Games, insisting that he never asked coach Luis Milla not to include him in the squad for the United Kingdom.
"I did not renounce to anything," the 24-year-old noted. "I always said I wanted to go, I spoke with the coach and he gave me his opinion.
"There were many team-mates of mine in the team and I really would have like them to win.
"They are a great team and they always proved it. But in such small tournaments, you cannot afford to make mistakes, and they lost the first two matches due to minor details."
Barcelona have been credited with an interest in Athletic Bilbao starlet Javi Martinez, who can play in Busquets' position, but the Blaugrana midfielder underline that he is not fearing for his place in the starting team.
"If a player who has the same characteristics as me or who can play in the same position arrives, he will always be welcomed," Busquets added.
"Whether the club sign anyone or not, I will continue to give my best to win a starting berth."