Pulis has come under fire from his own supporters following the Potters' slide down the Barclays Premier League table that has left them just three points above the relegation zone.
Redknapp struggles to comprehend why Pulis, who until this season had been viewed as having done an exemplary job at the Britannia Stadium, is in the crosshairs.
"Absolutely the criticism he's had is unfair. He's done very well and has taken the club to another level," Redknapp said.
"They established themselves as a good mid-table Premier League club. They're a good club, well run with a good manager.
"They have had a blip and I'm sure Tony is finding out know who his friends are. People desert you at times like this.
"When confidence goes it can very hard to put your finger on why it's not there. You look for answers to what has happened and they're not easy to find."