DERRY — As season-opening performances go, Pinkerton Academy head coach Brian O'Reilly gave his No. 2-ranked football team a less-than-mediocre mark.

And the Astros still won by three possessions.

“Team grade? It's a C-minus,” O'Reilly said when asked to analyze his Derry squad, which beat No. 4 Bishop Guertin of Nashua, 20-3, Saturday at Memorial Field. “The offense dragged this team's score down today. The offense was not good. And I run the offense.”

The defense was a different story. Hard-hitting linebacker Matt St. Onge led the group, which recovered four fumbles and recorded two interceptions.

“I felt we really picked up the slack, had some big plays, some picks, some fumbles. I thought we played tough,” said the senior, whose team finished plus-5 in the turnover margin (6-1).

Andrew Ong, Nick Liporto and Jake Bernaiche rotated into the defensive end slots — and consistently forced BG quarterback Tom Hurley to scramble.

BG had just one play go for a gain greater than 17 yards. Kevin Kiczuk's second-quarter speed sweep around the right corner went for 35 yards.

“They're a lot bigger than us up front. They've got some good linebackers that were able to disrupt things on us. I didn't think we could go straight at them,” said BG head coach Travis Cote, who dropped to 0-9 lifetime against the Astros.

Kiczuk's run led to BG's field goal, a 30-yarder from Steven Toscano. It cut Pinkerton's lead to 13-3.

Pinkerton (1-0) scored those 13 points in a blink.

Manny Latimore returned a second-quarter punt 66 yards for a touchdown. The junior ran across field to turn the corner along the Astros' sideline, then took off.

Guertin (0-1) fumbled the ensuing kickoff. The Astros covered 33 yards in four plays, highlighted by Chris St. Onge's 5-yard TD run off right tackle.

But Pinkerton ball carriers were largely contained. Penetration from lineman Pat Yourell led to multiple gang tackles for a loss. Linebackers Blake Boudreau and John Miller clogged space between the hash marks.

Neither offense established rhythm. Pinkerton, however, turned two BG fumbles into TDs. Matt St. Onge capped a three-play, 7-yard drive midway through the fourth.

“I have to give them credit for (their defense). But we struggled on offense today. Through the air, on the ground, outside, inside,” O'Reilly said. “But we'll fix it. I know that.”

Video -- Pinkerton FB/LB Matt St. Onge:


Video -- Marc Thaler's recap of the game:

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