The 29-year-old defender has urged his side to quickly bounce back from their defeat to west London rivals QPR when they travel to Anfield to face Liverpool on Saturday
The Rs earned their first Premier League win of the season with a 2-1 victory over Martin Jol's men at Craven Cottage on Saturday.
And the Irishman expressed disappointment at his side's lacklustre performance against their rivals before insisting upon an instant improvement.
"In the first half we never got ourselves into it," Kelly told the club's official website.
"We seemed to be on the back foot and never got going. They came at us and we didn't have anything to counter that.
"We got a goal towards the end we were pushing and pushing but it never came. Overall, we're disappointed for everyone.
"Come here, with it being a derby and being big rivals, we wanted to give the fans something to cheer like last season when we won here.
"They came out in their droves on Saturday and it's a shame we couldn't give something back to them. We've got to pick ourselves up and go on from there.
"It is something we have to learn from and look ahead to the next game. We've got a big match at Liverpool on Saturday. It's a tough place to go but we did well there last year."