The Hornets routed the rival Seahawks behind Dorian Johnson’s 20 points, including 14 in the fourth quarter. (Nick Plum for Synthesis/Koubaroulis LLC./The Washington Post)

As Herndon traded baskets with South Lakes midway through the third quarter of Friday’s rivalry boys’ basketball game, Dorian Johnson tried to hide his anxiety. Strapped with three fouls, the senior guard dutifully cheered on his teammates from the bench, but most of his time was spent intently staring at the scoreboard.

“I was so anxious to get out there because it felt like an eternity,” Johnson said. “With about four minutes left, I asked to go back in . . . but the coaches said as long as we had the lead, we were good. And we were.”

When Johnson’s moment did come about six minutes later to start the fourth quarter, he quickly made up for lost time, scoring 14 of his 20 points in the final period to lead No. 19 Herndon past South Lakes, 73-53, at home.

Driven by their raucous crowd, Herndon (6-2) played aggressively on both sides of the ball, leading to forced turnovers and numerous trips to the foul line. The Hornets shot 28 for 34 from the free throw line, including 13 of their last 14 to close out the game.

“Our free throws were big for us, and that’s something simple that we work on every day,” Hornets guard DeAndre Thomas said.

Just as big was Thomas’s play off the bench. The senior, who attended Potomac Falls last season before transferring back to Herndon, paced the Hornets in the third quarter, giving his team the lead for good at 32-29 with a three-point play after a strong finish.

Thomas (12 points) also joined with Herndon’s guards to contain South Lakes star guard Brandon Kamga (20 points and eight rebounds). Though the junior showed flashes on strong drives to the rim, Kamga was held to just four points in the fourth quarter as Herndon’s full-court press and double teams pushed him away from the basket.

“We knew he’s a great player, and we wanted to contain him,” Johnson said, “but we’re confident in what we do, so we didn’t want to change everything just for him.”

As Johnson attacked the rim in the fourth quarter, it was the Seahawks (2-4) who were left searching for answers. Following Johnson’s second three-point play of the period with less than three minutes to play, the Hornets drained their next nine free throws to outscore South Lakes 13-3 the rest of the way.

In addition to the crosstown rivalry at stake, Friday’s victory brought extra emotion for the Hornets, whose coach, Gary Hall, suffered a mini-stroke earlier this week. Hall, who attended Friday’s game and offered a few words of advice behind the bench, expects to return to the sideline soon.