Now the England striker wants them to put May 17 aside and end the Premier League campaign on a Fulham high.
The Blues have suffered three consecutive defeats going into Sunday's league finale.
Recent lacklustre performances have cost them the chance of finishing fifth and ninth place is now an alarming possibility.
Defoe is convinced the Cup final has been at the heart of their slump, with players allowing themselves to become unsettled by the Cardiff clash.
And the striker, who is cup-tied for the Wembley showpiece, has called upon his team-mates to raise themselves for one final league match.
He said: 'Fifth place was there for the taking really and we let ourselves down.
'Obviously we know we've got the Cup final and people are thinking about it. It's only natural.
'It's difficult really. Sometimes players get tired and think about the final, sometimes players might think they don't want to get injured.
'At the end of the day it shouldn't happen but it does.
'It's always at the back of your minds. I can't comment on other people. I don't know what everyone is thinking, but if I'm totally honest, if I was playing in the Cup final I would be thinking I could miss it.
'It's such a big day and as a footballer that's why you play football – to play in cup finals.
'It's a massive game and everyone is looking forward to it, not just the players but everyone involved in the football club.
'That's no excuse for the way we are playing lately but I'm sure it will pick up and it's time it did against Fulham this weekend.
'We've got try to be professional and think about gaining points in the league.
'We're at home and hopefully we can play like we did when I first joined, move the ball about, and get three points.'
Regardless of Sunday's result, Defoe still believes it's been a tremendous Premier League campaign for the Blues.
And with the possibility of a cup also on the horizon, he insists it's been one to remember.
He added: 'If you look at the season overall I think it's been a great one for the club.
'To be honest, even before I came the lads had done really well and to actually get to the Cup final is brilliant.'

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