By Seth Lakso, Globe Correspondent

Defending Division 1 state champion St. John’s Prep received a wake-up call to open its season last night, surviving a strong challenge from St. Mary’s before posting a 78-76 overtime win in Danvers.

“We told the kids before the game that they’re going to get everyone’s best shot,” said Eagles assistant coach John Dullea. “It’s going to be like this every game. Hopefully it’s a wake-up call that things aren’t going to be as easy for us this year.”

It took 38 points -- including 20 in the second half -- and 20 rebounds from senior Steve Haladyna for Eagles, who finished last season 25-1, to walk away winners.

Haladyna, who is just 41 points shy of reaching 1,000 for his career, has taken over the scoring load with the school's all-time leading scorer, Pat Connaughton, now playing at Notre Dame.

“It’s tough to replace a talent like Pat, but [Haladyna] can fill it up,” said Dullea. “He’s taken up the leadership role on this team and become more vocal. He did a lot to pump our guys up.”

The Spartans came out playing a two-three zone that gave the Eagles, who are used to seeing man defense, trouble early on.

St. Mary’s took a surprising 36-31 lead at halftime.

The Eagles, playing without starters Isaiah Robinson (torn meniscus), Owen Marchettie (sprained ankle), and Drex Costello (knee), settled down in the second half and carried a 5-point lead heading into the final three minutes.

“The injuries certainly aren’t helping us,'' said Dullea. "Once they get back we’ll have more scoring options.”

The Spartans rallied in the final minutes. Senior shooting guard Devin Thompson knocked down a deep three with just seconds remaining to send the game into overtime tied at 68.

Thompson finished with a team-high 28 points.

“St. Mary’s made some big plays,” said Dullea. “They came out intense and played like they had nothing to lose and whenever they needed a big shot it seemed like they hit it.”

In overtime the lead see-sawed, with both teams tiring in their first contest of the season.

With under a minute remaining, St. John’s Prep’s Mike Carbone connected on a three to put the Eagles up 2. The Spartans never recovered missing a contested three at the buzzer.

Senior Fred Shove was impressive for the Eagles, collecting 16 points and 16 rebounds in the place of Robinson.

Haladyna will continue his run toward 1,000 on Thursday when the Eagles host Lynn Classical.