The result leaves Real Madrid clear at the top of the table.
Busquets told Movistar that Barça "will keep trying while we have a mathematical chance" but his face told a different story.
He added: "Dropping two points in the fight for this title is to give the rival a big advantage. But for as long as we still have a chance, we're going to keep fighting.
"We were leaders before the break but we have dropped points. Today we showed up but for one reason or another we haven't for the three points and we will drift further from the title if Madrid win.
"But we have to focus on ourselves, even if it seems unlikely that they will drop points because they're doing really well."
Barça twice led against Atletico but two penalties converted by Saul Niguez saw the Rojiblancos leave Camp Nou with a point.
"We competed well but the two penalties penalized us," Busquets added. "And when you concede two against a team like Atletico, you have to do a lot to win. It's a shame."