Tueart won the 1976 League Cup with Manchester City and three years earlier was part of the Sunderland team that shocked Leeds United to lift the FA Cup.
He told Sky Sports News: "I thought at one stage during the first half of the season, we (City) were in danger of becoming a two-man team with Aguero and David Silva - two fantastic player, two world class players.
"If those two play, it will be really important to Man City and tough for Sunderland.
"Your big players have to perform and what will interest me is the strategy of the manager - we have got highly skilled individual players and I'm sure Manuel Pellegrini will want to get his first trophy in the cupboard.
"Gus Poyet has got a very well organised, very disciplined and a very work ethic team. So it will be a contrast of two different sides for me."
Dennis Tueart was speaking on behalf of Capital One, the credit card company and sponsors of the League Cup