Dr Helmut Marko says a "mistake" in the simulator prior to Singapore spoiled Red Bull's chance of victory.
Max Verstappen finished third behind the Ferraris, and when asked if there was a chance of a better result on a track that was expected to suit Red Bull, he answered simply: "No.
"I could make it a huge story, but no."
Marko, though, had a lengthier explanation for the surprising Singapore struggle.
"The problem was in the simulator. We were totally misled there," he told Austrian broadcaster ORF.
"The simulator is the basis of our setup for the race weekend, so if it is not right from there then you are in trouble.
"The problem is that we set up our chassis much too stiffly, which meant we lacked stability. We also had too little downforce," Marko added.
Team boss Christian Horner added: "It would have been worse if Mercedes had not made that strategy error."
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