Wells added eight rebounds and two steals for the Raiders (22-4), who advanced to the semifinals to face Milton on Monday, which beat Roswell in its first-round game.
Walton qualified for the Class AAAAAA state playoffs with its win over Lassiter.
“It wasn’t pretty, but we’ll take it,” Raiders coach Joe Goydish said. “Nick really came to play and came up big for us with his shot selection and rebounding. The guys were really active out there and I’m proud of them.
“When you’re 21-4 on the season, you expect to make the playoffs, so we’re glad we were able to advance.”
Walton hadn’t practiced for a week, but it didn’t show on the court. Divine Anyanwoke’s layup put Lassiter (5-21) in front 2-1 early, but the Raiders responded with a 10-0 run and closed the period on a 7-2 spurt to take an 18-6 lead at the end of the first quarter.
Chad Clay’s jumper with 1:45 remaining in the second period put Walton in front 32-12, but the Trojans closed with a 6-0 run and trailed 32-18 at halftime.
Walton outscored Lassiter 15-13 in the third quarter and both teams scored 17 in the final period.
“We defended well (Saturday), and that’s the reason we were able to win this game,” Goydish said. “Lassiter’s a gritty team and they’re our rival. They’re well-coached and made a nice run in third quarter when they cut it to 10. But our guys did what they were supposed to do and helped us move on.”
Elijah Weems added 12 points, three rebounds and four assists for Walton. Jay Bowyer, who had eight points in the fourth quarter, finished with 11 and chipped in four assists and two steals. Clay had eight points, four rebounds, four assists and two steals. Maurice Gibson scored eight off the bench.
Derrick Lloyd contributed 14 points, including seven in the fourth quarter, and had four rebounds and four steals for Lassiter. Evan Dunham collected 10 points, five rebounds and five steals, while Austin Cheatum, Justin Jackson and Anyanwoke each had six points. Cheatum also had six boards.