Losing games to Brockton, Mass. — which Division I Pinkerton Academy has done nine of the last 10 years — does not sit well with head football coach Brian O'Reilly.

Losing altogether the chance to play the powerhouse Boxers is a reality O'Reilly likes even less.

“Seventeen years. It's over,” said O'Reilly, whose No. 3 Astros (5-1 overall, 4-1 Div. I) tonight leave Derry for a date with the Boxers (3-2), the No. 8 Bay State squad in the ESPNBoston.com Top 25.

Brockton-Pinkerton — a rivalry dating to 1996 and once knotted through six games — is perhaps the biggest casualty of next year's major overhaul to NHIAA football. The decision to create a 20-team Division I and quarterfinal playoff round leaves all teams without an open date.

“I understand why we're doing it. I don't have a problem with realignment,” said O'Reilly, whose team travels to Marciano Stadium for a 7 p.m. clash. “It's just unfortunate … but the state comes first. The (Division I) championship comes first. If that's the way it is, that's the way it is.”

The 2013 format is experimental. NHIAA executive director Patrick Corbin said the football committee will evaluate the system — and make adjustments where necessary — upon conclusion of the campaign.

The guess here, though, is any potential changes after one year won't be so significant that Pinkerton regains its open date.

A future without Brockton doesn't make Pinkerton any less of a perennial contender. But it's hard to dispute that facing one of New England's storied programs gave the Astros an edge in the postseason.

“I would much rather lose a close game to Brockton than easily win a game against a lesser opponent, where all we do is show up and win,” said O'Reilly, whose lifetime record against the Boxers is 4-12. “I don't get that.”

Pinkerton won the first meeting, 26-20. Brockton was the New England Sports Network's No. 1 team.

Can the Astros win the finale to snap a five-game skid in the series?

“I'm not OK with losing the last (five) years. But I'm certainly going to miss playing them,” O'Reilly said. “They have been tremendous to us for 17 years.”

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HOW NO. 2 Exeter (5-1, 4-0 Division I) defends No. 6 Nashua South (4-2, 3-1 Division I) may be the top storyline for tonight's game on the Seacoast.

“It all starts with Trevor Knight,” Exeter head coach Bill Ball said of South's quarterback. “Their running backs are good. Their receivers get open. (Knight) has the ability to run and throw. You have to choose your poison.”

In Week 4, Concord applied constant defensive pressure to beat South, 20-3. Knight faced blitzes for four quarters.

“We pressure when it behooves us to,” Ball said. “But it's really not our style.”

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NO. 4 Bedford (5-1, 4-1 Division II) faces a foe far more competitive than its one-win record suggests.

Dover (1-5, 1-3 Division II) lost two weeks ago in double overtime to No. 1 Winnacunnet of Hampton, 31-24. The Green Wave last week lost at now-No. 5 Keene, 21-20.

“They're big. They're strong,” Bedford senior running back Dylan York said of the Green Wave. “We're hoping our speed will definitely be a factor.”

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ONE TEAM'S win streak of five games ends tonight in Amherst, where No. 9 Souhegan (5-1, 5-0 Division III) hosts Milford (5-1, 4-0 Division III).

Milford head coach Keith Jones is 1-10 lifetime against the Sabers.

“Trying to pour salt in the wound, are you?” Jones said via text.

The Spartans last Friday defeated Division I Nashua North.

“Going in to Souhegan, there will be a lot of emotion,” Jones said after the 24-21 win against North. “It's a big test for us, to see if we can harness our emotions, keep momentum and play well.”

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Marc Thaler covers high school football for the New Hampshire Union Leader & Sunday News. He co-hosts the “N.H. High School Football Show” Saturday 7-9 a.m. on Manchester's WGIR-AM 610 and the Seacoast's WQSO-FM 96.7. Send e-mails to mthaler@unionleader.com and follow him on Twitter: @marc_thaler.