Sinclair played with Cahill at Burnley.
He told the Lancashire Telegraph: "When John Terry couldn’t play last season you saw him and David Luiz two as being the two main centre halves. Gaz is quick and big and aggressive.
“He likes to attack the ball and when you have players like that around you it makes the game a lot easier.
“Gary is very similar to JT in that he is big and strong, but he is more mobile.
“He could go on to take his place at the club, and maybe in the England set-up as well.”