The Spain international joined the Gunners from Spanish club Malaga and has made an impressive start to life in the Premier League.
"Cazorla is a superb footballer and I think Arsenal have got a real diamond," Redknapp wrote in The Sun.
"However much they got for Cesc Fabregas, £40m or whatever it was, they have managed to replace him for less than half the money.
"I am a huge fan of Cesc, but I honestly don't think there is anything between the two of them. They're both top Spanish internationals — and Cazorla will be a truly great signing for the Gunners. Probably the best one any side made this summer, in my opinion."
Cazorla won the European Championship in 2008 and 2012 with Spain.