Manchester City manager Roberto Mancini has hinted that he will sign more players during the January transfer window.
The Premier League champions signed six players in the summer, including midfielder Javi Garcia and defender Maicon.
"If we want to stay on top with all the other teams that spend a lot of money in the last 10 years we need to improve and buy top players," said Mancini. "It is usually more difficult to stay on top.
"It can happen that you can win the title because you play well or because you are lucky. We deserved to win last year but the second year is always more difficult.
"There were a lot of teams in the past spending money for big players, including Arsenal. This is normal."
City will continue their defence of the league title with a home game against Arsenal on Sunday.
