The 19-time capped Portugal international marked his 133rd appearance for his boyhood club with his 12th career goal and admitted it was his last game.
"It was a very important game for me and being able to mark it with a goal was very special," he told Benfica TV after the game. "I believe that everyone already has an idea why I hugged Rui Costa."
The Citizens have agreed to let Nicolas Otamendi return to Benfica in a separate deal worth €15-million, according to BBC Sport as Guardiola looks to shore up his defence that's been the club's Achilles heel since the exit of Vincent Kompany.
City currently have John Stones, Aymeric Laporte, Nathan Ake and Eric Garcia as centre-back options but the latter is seemingly poised for a return to FC Barcelona.
Their defensive frailties were evident on Sunday as the Foxes romped to a 5-2 victory at the Etihad Stadium with Jamie Vardy scoring a hattrick.