Barcelona drew 1-1 away from home in the first leg of their Champions League round of 16 tie against Napoli.
Dries Mertens gave the home side the lead before Antoine Griezmann equalised for the visitors to take a crucial away goal back to the Camp Nou.
"[Nelson] Semedo and I were one booking away from a ban so we were always running that risk [of suspension]," Busquets told the media after the Napoli game.
"We hope Pique's injury is nothing serious but we will take on the second leg with what we have. We don't have a deep squad because, unfortunately, that's how it was planned."
Barcelona are already without first-teamers Luis Suarez, Ousmane Dembele, Jordi Alba and Sergi Roberto for the match against Real Madrid.
"We have a short squad but those that are in charge knew that," the Croatian midfielder said.
"The solution is what it is. Those that are available will have work really hard because we have an important match in the second leg."
The comments come not long after Lionel Messi's criticism of sporting director Eric Abidal, which almost cost Abidal his job.
"We can win La Liga and the Champions League," the coach said.
"It's true we've lost Busquets and Vidal for the return game but we will recover Alba and Roberto.
"I'm one of those people that looks at things optimistically. We don't have many players, but there's no point complaining about it."
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