Richardson had a game to forget after being thrown in at the deep end in Saturday's Barclays Premier League defeat at West Ham and was hauled off after an hour.
That was 24 hours after the midfielder's reported ?2million deadline-day switch from Sunderland and he told his new club's official website www.fulhamfc.com: "I was upset with the way the game went. I didn't feel sharp at all, I felt sluggish."
He added: "I hadn't really trained with the team so I didn't know the way they played that well but I've got a break now before the next game and I'll get my fitness up and understand more on how the team play."
Richardson, who was born in Greenwich and was on West Ham's books before joining Manchester United, was delighted to be back in London.
He said: "I'm so pleased. Me and my family are so chuffed to be here.
"I first heard that Fulham were interested in me towards the end of last season, so I've always had it in the back of my mind that I could be coming here.
"Finally, it did happen for me and I want to thank the manager and the chairman. I want to do well for the club and for the fans.
"I've spoken to the manager and we've had a good chat. I'm hoping he'll get the best out of me.
"Saturday was a bad performance but I've put that behind me and I'll be working hard on the training field to prepare for West Bromwich Albion."
Source: PA
Source: PA