Redknapp, who last managed against the Reds in 2015 with QPR, has been impressed by the improvements shown by United under the guidance of Erik ten Hag.
Speaking to United Review, the official match programme for this evening's game at Old Trafford, he picked out Lisandro Martinez as a player who has done particularly well so far this season, from the clutch of quality names who were brought in last summer.
“You can see real improvement, they [United] strengthened well in the summer,” said Redknapp.
“Lisandro Martinez has come in and done very well at the back.