The midfielder admitted Barca need to make new signings now, with the start of La Liga less than a week away.
Barca have been heavily linked with moves for Ousmane Dembele and Philippe Coutinho, yet it is Paulinho who appears closest to signing at the moment.
"We don’t need new signings because of the result, but because we have to renew [the squad]. And now’s the time, no matter what," he said via Sport.
Gerard Deulofeu filled in for Neymar against Madrid, but failed to shine, while the club’s only other summer signing, Nelson Semedo, did not feature at all.
Busquets also insisted Barca did not play too badly at Camp Nou, but did concede winning the trophy now, is highly unlikely, against a Madrid side in top form.
"The result is there and is unchangeable. But I think that we were not bad, we played quite well during some of the game and created more chances than them, but lacked accuracy,” he added.
“We dominated the play but they were clinical and when we left them space they were lethal on the counter. There’s no need for any excuses, now we have to draw up conclusions and look forward.
"We have the game at the Bernabeu on Wednesday. It’s almost mission impossible, it will be really difficult to turn it around but we will try."
This promises to be an intriguing week in the world of Barca. Whether we like it or not, it seems as though Paulinho will be presented this week, while we await updates on Dembele and Coutinho.