Exactly four months ago -- just 120 days -- these teams faced off in Game 6 of the World Series. The Yankees won easily, 7-3, for their 27th championship.
This game at certain-to-be-sold-out Bright House Field not only matches last year's two best teams, but also two of the game's top pitchers, both Cy Young Award winners.
It's so important that MLB.TV and Philadelphia's Comcast SportsNet will telecast it live, while the MLB Network and Comcast will rebroadcast the game in prime time.
Halladay, obtained by the Phillies from the Blue Jays in a December megadeal, will make his debut for the defending National League champions.
Sift through all this hoopla and the underlying a question is simple: Will these teams be able to repeat?
Yes, they're early preseason favorites to meet again, but it's a long way from Spring Training to the World Series.
"Once you win, there's a bull's-eye on your back," Phillies shortstop Jimmy Rollins said. "Everybody is gunning for you."
Once a team wins a title, it becomes much more difficult the second, or even third, time around.
Last year, Yankees manager Joe Girardi wore No. 27, a message to his players they would be going after their 27th World Series championship.
This year, Girardi is wearing No. 28.
The Yankees may be improved for 2010 with their offseason moves, but, even with their enormous resources, repeating will be no easy task.
The same is true for the Phillies, who have won the NL East three consecutive years.
Phillies skipper Charlie Manuel told me the other day that players often forget what it took to accomplish what they did the year before.
"You have to keep reminding them," he said. "To me, it's all about focus. They have to remain focused, and it's not always easy."
Even the best teams -- on paper -- don't win.
I believe you can blame it on parity to a degree, but free agency -- and the fact that championship teams often cannot afford to retain their premier players -- is also a key reason.
Girardi agreed that a combination of free agency and parity have made it so difficult for teams to repeat.
"I'm not a huge believer in the lack of focus," he said. "I know the taste of winning a World Series is so much better than the experience of never having been there. You don't realize how great it is until you get there. When you do it, I think you want to get back worse than before. You know how wonderful it is.
"The guys are hungry, and they want to get back, so I don't see how they can become complacent."
Girardi said the additional rounds of playoffs also make it more difficult. Prior to 1969, first-place teams (pennant winners) in each league went to the World Series. The two League Championship Series were introduced in '69, and the four Division Series (two in each league) were added in 1995.
World Series champions now must win 11 postseason games. It took just four before 1969.
Girardi said Hall of Famer Yogi Berra is often teased about his 14 trips to the World Series. He and the Yankees won 10 of them.
"You were automatically in if you finished first in your league," Girardi said.
Consider some of these numbers:
If the Phillies, who won in 2008, make it back this year, they'll become the first NL team since the 1942-44 Cardinals to play in three consecutive World Series.
The Yankees, who won their first World Series since 2000, have won back-to-back 12 times and went to the Fall Classic four consecutive years beginning in 1998.
"I didn't want the year to end," said Yankees third baseman Alex Rodriguez, who played in and won in his first World Series in 2009. "We just wanted to keep showing up. It's our job now to come back and find out niche."
But think about this:
Since 1997, in the NL, 10 different teams have gone to the World Series, and only the Phillies have been there in consecutive years.
How difficult is it to repeat?
In the past 30 World Series, 19 different teams have won. Only the Blue Jays in 1992-93 and the Yankees have done it in back-to-back years during that period.
After the Cincinnati Reds, the Big Red Machine, won the World Series in 1975-76, they didn't return again.
"You get off to a slow start, things don't go quite so well and all of a sudden you're trying to make up ground," Hall of Fame manager Sparky Anderson told me years ago. "Players began to press. Batters try to hit five-run homers. You just can't do that."
When the Yankees and Phillies take the field on Thursday, they'll probably be sizing each up for the 2010 World Series.
Keeping that date and making it happen will be no easy task.
Hal Bodley is the senior correspondent for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.