Following the 0-0 draw with the Swans, Mancini expressed his frustration at how his players had failed to make the most of their opportunities during the game.
And on the subject of negotiating league fixtures in the last few days building up to a Wembley trip, the Italian said: "It is difficult and (the Swansea match) was difficult as our concentration is on the final.
"But we need to play these games and for us it is important to win."
Mancini has emphasised that it is far from ideal to have to play four days before a cup final, but acknowledged that Wigan - who host Swansea tonight - are in the same boat.
"It would be better to have one week (of unbroken preparation)," Mancini said.
"But we play Wigan and it is the same for them. Then we have four days to prepare."