That Yankees team won it all behind two elite playoff starters (David Cone and Andy Pettitte), and a lights-out back of the bullpen that featured Mariano Rivera setting up John "Protected" Wetteland. Together, those two guys functionally lopped the last two innings off playoff games, and put a ton of pressure on opposing offenses to score early.
Those four pitchers were good enough to lift an otherwise average offense to a title. The Yankees team OPS+ for the season was only 99, and New York finished 9th in the American League in runs scored with 871, 162 behind the league-leading Mariners. Heck, the team's highest-paid hitter (and highest-paid overall player, in fact) was midseason acquisition Cecil Fielder, who would be edged permanently out of the league and wedged permanently into a booth at Stuckey's just two seasons later.
The Sox already had two elite postseason starters in Josh Beckett and Curt Schilling (with, I suppose, Dice-K filling the Jimmy Key role if you want to push the analogy). With the Gagne trade, the Sox now can alternate Gagne and Hideki Okajami in the Rivera/setup role, and reduce some of the wear and tear on Wetteland clone Jon Papelbon. It's sort of a neat approach, and is a very different way of constructing a team than the Sox' pre-Theo method of assembling 9 guys the size of Jack Clark and turning them loose on the league.
Also, as is obvious from the picture at left, the Sox can also now platoon Gagne and Julian Tavarez at Designated Ugly Guy. That platoon will probably be enough to lead the league in ugly now that Randy Johnson is out for the season.
But the really cool part is that the Sox likely didn't give up much to get Gagne. Kason Gabbard aspires to have Aaron Sele's mid-period career as a starter who varied between acceptable and useful, depending on whether he could thrown his big curveball for strikes. David Murphy is a tweener OF who has Terrence Long on his list of BP comps.
And Engel Beltre is . . . well, nobody knows exactly what he is. He's all of 17, and apparently is toolsy. That's not all that helpful, of course--Toe Nash was toolsy as hell, and I believe that at the moment he's a part-time crab shucker in Bogalusa.
At any rate, it looks like Sox are going to hope that their offense, which is much weaker than the '03-'05 editions that made it to the playoffs, can outscore their opponents if it has a two-inning head start. I have to say, that makes a certain amount of sense.