As it turned out, the day newly acquired slugger Carlos Beltran joined the San Francisco Giants, the team was in Philadelphia at Citizens Bank Park — the same building where, nine months earlier, they had clinched a trip to the World Series by steamrolling the Phillies in the National League Championship Series, and the same building where, if we’re lucky, a rematch could occur less than three months from now.

Phillies Manager Charlie Manuel says Tim Lincecum is a good pitcher. (Drew Hallowell/GETTY IMAGES)

Is it instructive to point out the Giants have now beaten the Phillies in five of their last seven head-to-head meetings, dating to Game 3 of last year’s NLCS? Or that, since the start of the NLCS, Tim Lincecum and Matt Cain, the Giants’ top two starters, are a combined 4-1 with a 1.31 ERA against the Phillies — holding Phillies hitters to a combined .174 batting average? Perhaps.

“They’re good pitchers,” Phillies Manager Charlie Manuel told reporters, ceding no ground to Lincecum and Cain. “You say they’re great pitchers. To me, I don’t know how great they are. As they move on into their careers, the longevity part — I think that’s when the greatness might come in. I saw . . . good pitching. But at the same time, we can beat that. I’ve seen us beat that.”

At the very least, the events of the past week — both the Giants’ trade for Beltran and the results of the three-game series — should have served notice to the Phillies’ management that the Phillies, like the Giants, owe it to their fans to do everything possible to position the franchise for a World Series title in 2011.

The general manager of a contender has two main jobs — to take advantage of the team’s current championship window, and to keep that window open for as long as possible. Sometimes those goals can be at cross-purposes, such as in the case of a difficult decision to mortgage a piece of the future for an enhanced opportunity to win now. That’s what the Giants did this week by sending top pitching prospect Zack Wheeler to the New York Mets in exchange for Beltran. (It probably didn’t hurt, in the Giants’ internal deliberations, that Beltran is a lifetime .298 hitter, with five homers and 16 RBI, combined, against Halladay, Lee and Cole Hamels.)

If the Phillies — whose need for a right-handed bat is not as acute as that of the Giants’, but is painfully evident nonetheless — are going to pry away outfielder Hunter Pence from Houston, they will have to sacrifice an even bigger part of their own future — as many as three or four top prospects. Pence’s price tag is higher than that of Beltran because he is younger, and more importantly is under team control through 2013. That happens to be roughly how long the Phillies’ current window is open.

“I look at our situation,” Manuel told reporters, “and I see a window with our pitching and our core players, I see about a two- or three-year solid time to win . . . It’s harder for me to look any further down the road than that.”

There remains a good argument for the Phillies to do nothing at the trade deadline. It goes like this: Even after the Giants’ trade for Beltran, the Phillies are clearly the best team in the NL. Their run differential of +99 (through Thursday) is more than twice that of anyone else in the NL (the Atlanta Braves check in at +46) and is more than five times better than that of the Giants (+18). Their back-to-back losses to the Giants this week were their first since the first week of June. And of course, the Phillies’ projected starters in Games 1, 2 and 3 of any postseason series — Halladay, Lee and Hamels — are better than those of any other contender, including the Giants.

But the argument in favor of making a big trade is even stronger: The Phillies have a clear need for a bat. They have the prospects to make it happen. They have a defined window for winning championships. They need to take advantage of it. And as this week proved, the Giants were willing to make that same plunge — making a very strong team even stronger.

Oh, and just in case this week didn’t provide enough information about the relative strengths and weaknesses of the Phillies and Giants, they meet again for four games in San Francisco, beginning Thursday.