Manchester City boss Manuel Pellegrini expects a more difficult game than the one in September when his side faces Sheffield Wednesday for the second time this season.
The Citizens eased past the Owls by 7-0 when the two teams played in the Capital One Cup with all goals coming in the second half of the game.
But the Chilean expects a tougher challenge in the FA Cup, a competition City will be determined to win according to the manager.
"It's been a difficult fortnight with three games each week and December has been a key month, especially when we had to play for nine points in one week," Pellegrini said.
"We've got those games out of the way now and have won ten of our last 11 games but now we are only thinking of Sheffield Wednesday and the FA Cup.
"We had a good victory over Sheffield Wednesday earlier in the season but that game will not affect this one and we expect a difficult match on Sunday.
"It is a very important cup for us and last year we were disappointed to be eliminated at our own ground to Wigan Athletic in the quarter-finals, whereas we won the Capital One Cup.
"This year we have been eliminated from the Capital One Cup, so that puts an even greater focus on the FA Cup and we'll be trying to go as far as we can in this competition.
"Our form at the moment is very good and has been for the past two months so we want to keep that going as long as possible.
"We were making mistakes at important times but we made some minor changes and things began to improve.
"Some important players returned to their normal levels of performance and I'm very happy with the way things have been going.
"We still have a number of players injured but we are finding different ways to continue our good form."
