It was a gamble which did not pay off as Cesar looked ill at ease dealing with any passes back to him, and his failure to hold shots from Nathan Dyer and Rangel led to Swansea's first two goals.
The Brazilian should also not have been beaten by Hernandez from a very tight angle.
Redknapp said: "We gave some bad goals away, I can't look at them and say they were particularly good, there were some bad errors today.
"Our keeper has been fantastic, probably as good as any goalie in the league, but he played with a groin strain because he felt he was okay but obviously he wasn't at his best today.
"He felt he was fine and I can only go by what he tells me, I was told he was okay.
"He had a problem kicking and obviously when we passed the ball back he got himself under pressure.
"But in the previous five games when we have done well he has played well, but he had a bad day, that's how it goes."