The Rays and Red Sox, after a season of circling one another, neither able to shake the other, will commence the most important set of games they’ve played tonight. The Red Sox know and understand this time of year better than any team in the league. The Rays are here for the first time. It may still be difficult to believe the traditionally inept Rays are here. But, given their young talent, it will not be the last time.

The team with more wins than any of the surviving four clubs is also the youngest in the major leagues. The Red Sox-Rays rivalry, more intense this season than ever before, could become a commonplace occurrence, the next Red Sox-Yankees postseason feud.

“Well, I don’t really know about a rivalry,” David Ortiz said. “It’s their first year in the playoffs. I know one thing: If those kids stay out of trouble, they could do a lot of damage in this division.”

Baseball has been trending toward youth for a few seasons now, and the Rays have navigated in that direction better than any other team. The average age of the Rays' players who appeared in an ALDS game was 27.6. The Red Sox aren’t far behind – their average age in the ALDS was 28.5.

Seven of the eight scheduled starting pitchers are 28 or younger. (Only Tim Wakefield, 42, breaks the trend.) James Shields, at 26, is the grand old man of Tampa Bay’s starting rotation.

“Hopefully this isn’t the only time we’re going to meet in the playoffs,” Dustin Pedroia said. “It’s definitely fun playing these guys during the year. It’s going to be a dogfight.”

The teams never strayed more than a handful of games away from one another in the American League East standings all season. The Red Sox fought to hold on to their supremacy. The Rays fought for inclusion. Sometimes, they just fought.

“Someone is going to get the upper hand this series,” Tampa Bay outfielder Jonny Gomes said. “It’s going to be talked about when we play each other in spring training again.”

But first, starting tonight, they’ll play some slightly more meaningful games.

“It’s official,” Gomes said. “It’s not going away.”