The Argentine was at fault for Alaves' second goal as his poor clearance allowed Ibai Gomez to restore his side's lead, but Iniesta leapt to the defence of his team-mate.
"Football is all about success and mistakes. What happened to Mascherano could have happened to anyone," Iniesta told reporters.
"It was one of those games where nothing came off. We didn't do things well and we've paid with a defeat and the loss of three important points.
"Of course this has been a bad performance, but now it's about analysing the causes and correcting the errors.
