The St. John's field hockey team celebrates its win over Good Counsel in the WCAC championship. (Gabe Hiatt/For The Washington Post)

St. John’s field hockey Coach Corey Samperton had been on message for two months.

She declared it during Sunday practices, delivered it after the Cadets lost to Good Counsel in the regular season and reiterated it again shortly before the team met the Falcons for a rematch in the Washington Catholic Athletic Conference tournament championship. She delivered the message again at halftime during Thursday’s final at O’Connell.

By the time the sun set in Arlington, Samperton did not have to tell them St. John’s would win the WCAC title. The Cadets had a hulking trophy and a 2-0 victory to prove it.

“It makes us really want to win,” said junior Gena Witt, who scored an overtime goal in Tuesday’s semifinal with Holy Cross.

“Today we all came into school, and we were like, ‘We are all champions today. Within 12 hours we will win. We will be hall of famers. We will get the trophy. We will win.’ ”

On Friday morning, Samperton sent an e-mail to players and their parents that read, “Today is going to be the greatest day of my life. I believe that I am a champion.” She told the girls before the game that if they believed in their heart, half of their work was done.

“They have no idea what’s about to hit them,” Samperton said in the pregame huddle.

St. John’s (14-2) believed, applying pressure and forcing a timeout from Good Counsel (11-3) in the first five minutes while a booming black bass drum urged them on.

The Cadets fired out of the cage to stymie five consecutive Falcons corners in a first-half sequence, deflecting shots before they could reach senior goalie Katie Wright, who finished with 10 saves.

“They brought everybody,” said Good Counsel Coach Theda Bagdon, whose team went undefeated in the WCAC regular season. “There was more red back there than white.”

Freshman Clara Morrison gave the Cadets the lead with a short goal struck within a frenzy in front of the net 12 minutes 34 seconds before halftime.

A one-goal margin against a team that won the regular season meeting, 3-0, did little to calm the Cadets. But junior Ali House drilled a shot deflected into the goal by a Good Counsel defender on a corner with 17:24 remaining, and Samperton’s prophecies were coming to fruition.

“Right from the start of the season, it’s, ‘We’re starting today to get to the championship in two months,’ ” House said. “And then it became one month, and one month became a week, and now we’re here.”

After the game, while the Cadets were still hugging and screaming in the background, Samperton finally stopped talking up her team. She had just reached the word, “teamwork,” when the girls dumped a cooler of ice water on her head.