The central defender has been far from at his best this season and Redknapp thinks his latest injury struggles have really affected his confidence.
As such, the Sky Sports pundit believes Manchester City will have a far from straightforward Premier League clash on their hands against Newcastle later today, when they host John Carver's side at the Etihad Stadium.
Indeed, the former midfielder feels Newcastle will be given chances by the champions and that Kompany is a particularly weak link the visitors can exploit.
"This year his confidence is really low and when the leader in the team is lacking belief it rubs off on the rest of the players. Newcastle will believe that City will give them chances," Redknapp said.
"City had a decent team out when Newcastle beat them 2-0 earlier in the season in the Capital One Cup fourth round, their first win at the Etihad in 12 attempts. Despite being a mid-table team, they show glimpses. This won’t be straightforward."
The Magpies have only won once since Carver took charge as manager on a permanent basis, while Manchester City would be considered heavy favourites on paper, especially considering their recent 4-1 win at Stoke City.
As Redknapp suggests, however, Newcastle have already beaten them at the Etihad this season, while Burnley and Hull City both took points off City on their turf by adopting a defensive approach.
Can Newcastle do the same? And will Kompany prove the liability Redknapp believes he may well be for Manuel Pellegrini's men?