Last October, when the Boston Red Sox needed their best pitcher on the mound to open postseason play, they turned to Jon Lester. When they needed to open the American League Championship Series with someone who could shut down the powerful Detroit Tigers, they turned to Lester. When they needed someone to start the World Series, and then someone who could break a two-games-apiece tie in Game 5 in St. Louis, they again turned to the left-handed Lester.

It is almost unimaginable, then, that the tradition-rich Red Sox, with a devoted and emotional fan base that clings to its heroes like socks cling to towels coming out of the dryer, were in the position they were Thursday. Lester – cancer survivor, two-time World Series hero, homegrown product, ace – became the fulcrum of baseball’s trade deadline.

Yet the deal that sent the 30-year-old from Boston to Oakland, along with veteran outfielder Jonny Gomes, for outfielder Yoenis Cespedes perfectly exemplifies where baseball is at the moment: In any given season, any franchise could be either buyer or seller. NFL-style parity is upon us, and might be here to stay.

Consider this, first, from the Athletics’ side. Oakland, with the best record in baseball, has told rival executives that it believes it has a two-year window to win it all. The A’s acted as such earlier this month when they traded prized shortstop prospect Addison Russell to the Chicago Cubs for right-handers Jeff Samardzija and Jason Hammel. The message they delivered throughout baseball: Win now.

Thursday’s move to add Lester simply puts that message in boldface. Wednesday night, Hammel pitched poorly – again – with Oakland. He has yet to complete six innings and has a 9.53 ERA with the A’s, who have lost each of his four starts. Thursday morning, he had a new teammate that bumped him to the back of that rotation.

And take a look at that rotation now. Before Lester even arrives, Oakland’s starters lead the American League with a 3.32 ERA. Sonny Gray is 12-3 with a 2.65 ERA, a second-year stud who has just 31 major league starts — and no longer has to carry the burden of being the staff leader. Scott Kazmir, a reclamation project at 30, is 12-3 with a 2.37 ERA, one of the best stories in baseball.

Add Samardzija, who has 27 strikeouts and four walks while allowing hitters a .203 average in his first five starts for Oakland, and Lester, who has a 2.11 ERA in 13 postseason appearances and a nearly 5-to-1 strikeout-to-walk ratio this season, and suddenly Hammel doesn’t have a spot in a postseason rotation. Thus, with another deadline-day trade Athletics General Manager Billy Beane can turn lefty Tommy Millone into outfielder Sam Fuld, the former Minnesota Twin who will now, presumably, split time with Gomes in left field.

The losses for Oakland are significant. Russell is widely considered one of the top 10 prospects in the game, and had to be the hardest with whom to part, and they have Samardzija locked up only through next season. Cespedes, 28, led the Athletics with 46 extra-base hits, and he’s gone for two months — plus a postseason, presumably — of Lester.

But Cespedes signed a four-year deal with the A’s as a free agent from Cuba, and a clause in his contract allows him to become a free agent following the 2015 season, when he’ll make $10.5 million. So Oakland wasn’t likely to have him forever anyway.

As promising as Russell is — he’s currently destroying Class AA pitching at a .313/.352/.566 clip in his first 21 games in the Cubs organization — and as difficult as it can be to part with an established commodity, the A’s are better for these deals. If they entered the final week of July as a World Series favorite, they only solidified that standing Thursday.

The flip side of this discussion lies in Boston, where the Red Sox somehow finished last in 2012, won the World Series in 2013 — when every single move they made worked out — and are almost certain to become the first worst-to-first-to-last team in major league history. Yet in 2015, they expect to contend again. In a sport more conditioned to slow builds and sustained periods of success by the best organizations, this is unusual volatility.

But baseball has taken extraordinary measures to establish some sort of parity. Revenue sharing has helped the teams in the smallest markets compete financially. The game is extraordinarily healthy, with all 30 franchises making money. The most recent collective bargaining agreement established “competitive balance draft picks,” which are sandwiched between the first and second rounds of each June draft and are distributed among the teams in the 10 smallest markets, and those with the 10 lowest revenue streams. Those picks are the only choices in the draft that can be traded, and indeed, Oakland sent theirs to Boston in the Lester deal.

The Red Sox are in no way, shape or form a small-market team that needs help with payroll or revenue. But they are in position to show how a trade-deadline seller one year could be a trade-deadline buyer the next, possibly a true contender again. Cespedes, who has 17 homers, adds power to a Boston outfield that has combined for 17 all year. Put him alongside rookie center fielder Jackie Bradley Jr., and Boston suddenly has an athletic, spry outfield with two absolute rocket arms.

Consider, too, what they did later Thursday, sending right-hander John Lackey to St. Louis for first baseman-outfielder Allen Craig and versatile, 26-year-old right-hander Joe Kelly. That gives the Red Sox two more players under team control through at least 2017. They are, amazingly, a better team than they were 24 hours earlier. And what if they pursued Lester in free agency?

Table that for a moment. Twenty teams began Thursday either sitting in a playoff spot or within six games of one. With the moves flying, baseball had created hope in at least that many markets, and excitement throughout the sport. Mortgage pieces of the future for now? In Oakland, it feels like the right thing to do. Overhaul a team that won the World Series nine months ago so that it might be in position to contend nine months from now? In Boston, that feels right, too.