PHILADELPHIA -- Next up for Roy Halladay?

Putting on a Phillies jersey at a news conference at Citizens Bank Park.

Halladay on Tuesday reportedly passed a physical and agreed to an extension that will keep him in Philadelphia at least through 2013, and the ace's official introduction to Philadelphia is expected to happen on Wednesday.

With the final touches of the much-discussed four-team trade seemingly complete, the path is cleared for the Phillies to send prospects Kyle Drabek, Michael Taylor and Travis d'Arnaud to the Blue Jays, who are sending Halladay and $6 million to the Phillies.

Of course, the deals hardly end there.

The Phillies are sending Cliff Lee to the Mariners for prospects Phillippe Aumont, Tyson Gillies and J.C. Ramirez.

The Blue Jays are flipping Taylor to Oakland for Brett Wallace.

Four teams.

Nine players.

Two Cy Young winners in their primes.

Got all that?

ESPN.com reported that Halladay will receive $20 million per year in 2011, 2012 and 2013. The extension also includes a $20 million vesting option for 2014 based on innings pitched, games started or both. The Phillies required an extension with Halladay to make the trade.

So how did this all happen?

And why trade Lee?

It is clear the Phillies have wanted Halladay for some time. They tried hard to get him in July, but found Toronto's price too steep. Instead, they sent prospects Jason Knapp, Carlos Carrasco, Jason Donald and Lou Marson to Cleveland for Lee and outfielder Ben Francisco.

But the opportunity arose again to acquire Halladay, and Phillies general manager Ruben Amaro Jr. pounced. Amaro perhaps was nudged a bit more in Halladay's direction because he believed Lee would have been difficult to lure into a contract extension. Although Lee's agent, Darek Braunecker, said they only had preliminary talks with the Phillies, the feeling is that Lee would have required a CC Sabathia-type contract to remain in Philadelphia.

So once it became clear the Phillies could get Halladay, they started to shop Lee.

The Phillies traded Lee for a couple of reasons:

1.) They needed salary relief, even with the Blue Jays sending the Phillies $6 million, because they are pushing the limits of their $140 million payroll. Lee makes $9 million next season. Subtract his salary and add the $6 million from Toronto, and the Phillies are paying just $750,000 more for Halladay, who makes $15.75 million next season. Of course, if this was just about money, the Phillies could have traded right-hander Joe Blanton instead. Blanton could make more than $7 million next season in salary arbitration, which would have made the difference between Lee and Blanton around $2 million. That is relatively negligible when talking about keeping Lee in the rotation, which makes it clear that this move was much more than money motivated.

2.) The Phillies also traded Lee because they felt they needed to restock a farm system that has seen Amaro trade seven top prospects since July. Aumont and Ramirez are top pitching prospects. Gillies is a talented outfielder. Whether they develop in talents comparable to what the Phillies gave up to get Halladay and Lee remains to be seen, but the Phillies clearly believed they needed to take the opportunity to replenish.

In essence, this trade was not about taking one big shot in 2010, which keeping Lee would have allowed the Phillies to do. It was about upgrading the rotation, and keeping the organization competitive beyond next year.

Regardless, this is one of the biggest trades in recent memory. And the Phillies are banking that it helps them become the first National League team to play in three consecutive World Series since the 1942-44 St. Louis Cardinals.