Segura claimed Pique's error was "decisive, it changed the game completely", after the defender diverted Marcelo's cross into his own goal to break the deadlock at the Nou Camp in Sunday's first leg.
Busquets, however, said Segura should not have focused on his team mate after the heavy defeat by Barcelona's rivals.
"The play (Pique's own goal) was bad luck. We lost 3-1 because we committed some errors and they were very good when it came to finishing," Busquets told a news conference on Tuesday.
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"You don't lose because of one play. (This is) not the way to express yourself and even less so from inside the club, singling out a player."
Busquets said Barcelona needed to make signings after the first-leg defeat and reiterated that on the eve of the return at the Santiago Bernabeu.
The Catalans on Monday agreed a 40 million euros ($46.95 million)deal to sign Guangzhou Evergrande midfielder Paulinho.
Busquets, however, is still hoping for further reinforcements, especially after Paris St Germain signed Neymar for 222 million euros earlier this month.
"There's only one Neymar. We have to look forwards," said Busquets. "With Neymar leaving we need, above all, attacking players.
Cristiano Ronaldo gegen Barcelona
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"We have a good team, we're capable of having a great season, that's what we're focusing on. We want to convince the fans but the off-the-field situation is not up to me. I hope a lot of signings come and that they are of the highest quality."
Coach Ernesto Valverde believes Barcelona can still win the Super Cup, saying his side do not feel weaker than Madrid.
"Clearly we start from behind, but looking at the statistics nothing is impossible," said the coach. "No… I'm not going to say (Madrid are superior).
"Maybe at certain times, as they showed on Sunday when they took their chances. But does that mean they're better than us? No, I don't think that's a conclusion which should be drawn."
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