Two of the top high school basketball teams in Northern Virginia had played nearly 32 minutes of another draining, thrilling, exhausting track meet Tuesday night, but in the last 15 seconds there was no drama. William Wilson knew he would dunk as soon as he corralled a loose ball at midcourt.

“Fast break — I was thinking, ‘This is my chance,’ ” Wilson said.

His flush sent a packed student section streaming onto the court and sealed No. 12 South County’s 64-58 win against Lake Braddock in Lorton. But once again, the outcome was in doubt until the final seconds, and once again, the teams proved themselves as worthy adversaries in arguably the best rivalry in Northern Virginia.

Make no mistake: South County (20-2, 9-1 Patriot District) is poised for another deep run through the state tournament, and the Stallions fully expect Lake Braddock (16-5, 7-3) to be waiting at every turn.

“When we play them, we just have that energy that we don’t have against any other team,” Wilson said. “It’s like something special. That’s what helps us play our best.”

South County and Lake Braddock played five times last season, with the games decided by three, three, three, 12 and seven points. The Bruins won four of them, dropping only the second regular season matchup. They won the district and region finals and eliminated South County in the Virginia 6A semifinals before falling in the state title game.

The Stallions, with seven seniors, hold the upper hand this winter.

These competitive games should be customary by now. The Stallions won a state championship in 2018 and played close games to get there. But each matchup with Lake Braddock is different.

“We went through it again last year,” South County Coach Mike Robinson said. “Now we’re going through it again. So each team is different, and it’s a trying time.”

Every minute Tuesday, the two teams scrapped. South County scored the first four points. Lake Braddock fought back with the next eight. South County took the lead for good with 5:44 left in the second quarter and pulled ahead by as many as 11. Lake Braddock drew within three in the final minutes and had a chance to tie. South County’s Cody Kellem intercepted a pass to quell the ­biggest threat.

Wilson gave South County an edge when he began exploiting a hole in the middle of Lake Braddock’s 2-3 zone and shot 5 for 7 in the second half on his way to 16 points. It was a small edge. The Bruins’ David Solomon countered by going 8 for 14 with 21 points and 13 rebounds. Turnovers were even, at 12 apiece, with Wilson’s last-minute swipe ­evening the balance.

South County left the court celebrating, and Wilson said later, “We just know we have to be ready to play them again.”