Then at AC Milan, the veteran midfielder says that he was set to follow Carlo Ancelotti to Stamford Bridge.
However, he was persuaded to stay by Milan owner Silvio Berlusconi before later moving to Juventus in 2011.
"It was August 2009 and I'd reached agreement with Chelsea, the club where Ancelotti had just come in as manager," Pirlo revealed in his autobiography - I Think Therefore I Play, which has been printed in English for the first time.
"Carlo was like a father and a teacher for me, a kind, friendly man who knew how to make things fun.
"I'd spent the best years of my career with him. If you're a player who wants to get on and give everything, you won't find anyone better than him.
"Carlo Ancelotti was my motivation for agreeing to head to London. But, in the meantime, Berlusconi had pulled out a second piece of paper.
"This time there were loads of names with ticks next to them, and one that had been circled. 'Stay. We've signed Huntelaar'. Klaas-Jan Huntelaar is an excellent player. He knows how to score goals, loads of goals and, at that point in time, he was playing for Real Madrid. But he's not the type of guy who's going to win the Ballon d'Or.
"'Listen, Andrea, you just can't do this, damn it. You're the symbol of Milan, a standard bearer for this team, and we've already sold Kaka. You can't jump ship as well. It'd be a terrible blow, to our image as much as anything. We can't have everyone leaving.'
"Ancelotti and I spoke a fair bit on the phone. He wanted to bring me to London at all costs, and cost was indeed the last hurdle still to be overcome. Insurmountable, as it transpired.
"Milan wanted too much cash, and they were also pushing for Branislav Ivanovic to be included in the deal. Chelsea hadn't the slightest intention of letting the defender go.
"As it turned out, I moved to Juventus. That's Berlusconi all over, though. He's theatrical and knows exactly what he wants. It's what makes him such a fantastic president and lover of pure, beautiful football."
Pirlo also revealed that he thought about quitting after AC Milan's 2005 Champions League loss to Liverpool.
"I thought about quitting because, after Istanbul, nothing made sense any more," he declared.
"The 2005 Champions League final simply suffocated me.
"To most people's minds, the reason we lost on penalties was Jerzy Dudek - that jackass of a dancer who took the mickey out of us by swaying about on his line and then rubbed salt into the wound by saving our spot kicks.
"But in time the truly painful sentence was realising that we were entirely to blame."
Also on the Champions League, Pirlo revealed his suspicions about Deportivo La Coruna's players after they beat Milan in the 2004 quarter-finals - coming from behind to win the second leg 4-0, which took them through 5-4 on aggregate.
"We'd won the first game 4-1 and the chances of us not going through were roughly equal to those of seeing Rino Gattuso complete an arts degree," Pirlo wrote.
"What struck me most was how they kept on running at half-time. To a man: no exceptions. When the referee, Urs Meier, blew his whistle they all shot off down the tunnel as if they were Usain Bolt. They couldn't stand still even in that 15-minute period designed specifically to let you draw breath or at most just walk about.
"We were chasing shadows all night. Their players were crazy buzz bombs flying around all over the place. I don't have any proof, so what follows isn't an accusation - I'd never allow myself to go that far. It's simply a nasty thought I've occasionally let percolate in the intervening years.
"For the first and only time in my life, I've wondered if people I'd shared a pitch with might have been on something."