Damien Duff has completed his £17 million move to Chelsea from Blackburn Rovers.
The Republic of Ireland winger has signed a five-year deal reportedly worth £70,000-a-week.
He becomes new owner Roman Abramovich's fourth signing in two weeks.
"This was probably the biggest decision of my life and I didn't want to rush it," Duff said.
The Dubliner raised speculation that Manchester United might come in with a counter-bid after asking for the weekend to think over his Chelsea move.
He added: "It was just a matter of thinking everything through. I had seven great years at Blackburn and there was no big reason to move but in the end I decided a big new challenge was necessary."
Duff (24) will link up with Chelsea in the next 48 hours and fly to Malaysia where his new team-maters are taking part in the Premier League Asia Cup.
He said: "I'm really looking forward to meeting them all and playing for my new club. It looks as though great things are going to happen at Chelsea."
Duff's signing takes new Chelsea owner Roman Abramovich's spending to £36.9 million in less than a fortnight.
Geremi, on loan at Middlesbrough last season, was the first to arrive for £6.9 million shortly followed by Johnson for £6 million. England full-back Wayne Bridge joined from Southampton earlier today for £7 million.
