PORTLAND -- The Red Sox-Yankees rivalry has taken a break in 2008, with the emergence of the Tampa Bay Rays and the decline of the Yankees.

But in the minors, the rivalry continues.

The Portland Sea Dogs and Trenton Thunder, Double-A affiliates of the Red Sox and Yankees, respectively, face each other in the Eastern League playoffs for the fourth straight time, when the teams begin their best-of-5 Northern Division Series tonight in Trenton.

Triple-A also has a Red Sox-Yankees flair with Pawtucket hosting the Scranton/Wilkes-Barre Yankees.

The Portland-Trenton winner plays the Southern Division winner, Bowie (84-58) or Akron (80-62), for the league championship next week.

Trenton (86-54) is the defending league champion and this Thunder team looks formidable. They finished 12 games ahead of Portland (74-66), and beat the Sea Dogs 13 out of 21 games.

"I'm sure they're the team to beat," Sea Dog manager Arnie Beyeler said. "They won more games than anyone.

"We're excited to go down and get an opportunity, even though on paper it looks like we're the fourth seed."

The Sea Dogs will embrace that underdog role without fear.

"We got confidence to go out and beat these guys," said pitcher Dustin Richardson. "We got some good arms lined up and out hitters are seeing the ball well."

Trenton's strength is pitching, with a league-leading ERA (3.13). But Portland (sixth with a 4.29 ERA) will send two aces in Trenton.

Kris Johnson (8-9, 3.63) starts tonight. He has been with Portland all season, and has faced Trenton five times (1-1, 1.42 ERA). Johnson has had some tough luck collecting wins. In his last four losses, teams have scored a total of 10 earned runs off him.

Portland's Game 2 starter is its wild card. Clay Buchholz, who a year ago at this time was still basking in the hubbub over his no-hitter at Fenway Park, will get his third start for the Sea Dogs since being demoted by the Red Sox.

He scuffled in the majors, but is mowing down Double-A hitters (1.80 in two starts).

• Trenton's pitching features some potent starters, including Eric Hacker (7-4, 2.76) who goes tonight. Hacker is 1-0 (3.27 ERA) in two starts against Portland. He has not allowed more than two earned runs since yielding three runs July 19 against the Sea Dogs.

Hacker left after three innings in his last start, after taking a batted ball off his knee. But he appears to be fine now.

Game 2 starter Jeff Marquez, the Yankees No. 7 prospect, according to Baseball America, came down from Triple-A and is 1-1 (2.93) in three starts. Trenton's ace, Jason Jones (with a 3-0 record and 1.04 ERA against Portland) pitched Sunday and is not available until Game 3 on Friday in Portland.

• Portland's batters accounted for a .267 average, fifth best in the league (behind Trenton's .268). Portland has a mix of yearlong players, like Zach Daeges (.307, 63 RBI) and Aaron Bates (.276, 68 RBI), to go with mid-year promotions Lars Anderson (316), Argenis Diaz (.288) and Jorge Jimenez (.270).

• Trenton's batters are led by their outfielders -- Edwar Gonzalez (.295, 14 home runs), Austin Jackson (.285, 69 RBI) and Colin Curtis (10 home runs, 71 RBI).

While Trenton gets the home-field advantage in this series, the Sea Dogs have a winning record at Waterfront Park this year (7-6). The Thunder dominated at Hadlock Field (7-1).