The Reds have lost three of their first five games this season, and were beaten 3-1 by West Ham United on Saturday evening.
A new-look defence has struggled at times this campaign, and Redknapp thinks that they have looked as though they have been "gripped by fear".
"They've let in 35 league goals and kept six clean sheets in 2014. That's not good enough. Opposition teams are sensing the fear and set pieces in particular are now a phobia for Rodgers's men.
"The Liverpool defence look gripped by fear at every corner and free kick. Since the start of last season they have let in more goals from set-pieces than City or Chelsea. They must improve."
Brendan Rodgers's side host Middlesbrough in the third round of the League Cup on Tuesday evening.