Before R.A. Dickey can become a Blue Jay, he must finish talking turkey.

The Mets and Blue Jays have a deal in principle, a source said yesterday, that will send the NL Cy Young Award winner to Toronto contingent upon him reaching agreement on a contract extension with his perspective new employer.

A major league source confirmed Dickey and his camp were granted a 72-hour window on Saturday to negotiate an extension with the Blue Jays. That window would remain open until 2 p.m. tomorrow.

If the extension gets completed, the Mets are expected to receive stud catching prospect Travis d'Arnaud, pitching prospect Noah Syndergaard, catcher John Buck and an additional non-elite prospect. Josh Thole and a non-elite prospect would be expected to join Dickey in heading to Toronto.

The 38-year-old Dickey is signed through next season for $5 million. In discussions with the Mets he was seeking an additional two years and $26 million, but also made it clear last week he was offering a hometown discount of sorts.

So extension talks with the Blue Jays are expected to approach if not surpass $30 million over the same two years.

The 23-year-old d'Arnaud is the key to the deal for the Mets, who have struggled to find a consistent frontline catcher in recent years. The Blue Jays want Thole in the deal because of his experience handling Dickey's knuckleball. But to make that part of the deal happen, the Mets needed Buck, who arrived to the Blue Jays last month as part of their mega-deal with the Marlins. Buck will make $6 million next season, but the Blue Jays could defray some of the cost by including money as part of the trade.

D'Arnaud is regarded as the best catching prospect in baseball, but one major league talent evaluator who watched him play at Double-A New Hampshire two years ago wasn't overwhelmed by his skills.

"I liked him, but he was third in the Eastern League on my list as far as catchers," the evaluator said. "He's defensively solid and he's got some power, but to be honest I wasn't overly impressed with the guy."

D'Arnaud played 67 games at Triple-A Las Vegas last season and batted .333 with 16 homers and 52 RBIs, playing in a league known for offense, before a torn posterior cruciate ligament in his left knee ended his season in June.