Fox, in his 15th season at UNC, also rearranged his batting order by moving Brian Holberton into the cleanup spot and sliding the struggling Skye Bolt down to the 6-hole. Michael Russell also moved down one slot to the 7-hole.
Holberton made his coach look like a genius with a two-run home run over the right field wall in the top of the first inning. The home run, the junior catcher's 12th of the season, came on a 3-2 pitch and represents just the second in seven College World Series games thus far.
"I told myself he's going to try to throw a two-seamer in here, so don't get beat in," Holberton said. "He threw it in and I put a pretty good swing on it."
Fox, as usual, wasn't willing to take credit for the lineup adjustment.
"It made the move look good, but it wasn't me," Fox told reporters during his postgame press conference. "Brian's been in that position before. We felt we needed to move some things around a little bit, and really we did think about that, that having Brian in there, he can do a lot of things for us besides hit a home run. Obviously he can hit and run and he can bunt and he can do a lot of things for us. It paid off today. He did well."
UNC increased its lead to 3-0 in the third on a Colin Moran RBI single, which proved to be enough of a margin for Thornton (12-1, 7.0 IP, 9 hits, 2 ER). The rookie performed like a veteran in his first College World Series appearance, forcing three fly balls with multiple runners on and two outs.
With runners on first and third and no outs in the seventh, an "LSU" chant rose from the TD Ameritrade Park crowd as All-American Alex Bregman stepped to the plate with his team trailing 4-1. Despite falling behind in the count, Thornton forced a 6-4-3 double play to alleviate the situation by only allowing one run to score.
"He was just terrific," Fox said. "He made some big pitches when he needed to, and kind of weathered the storm a little bit, big double play there, big pitch here, which was critical for us."
Thornton's 12th win set a school record for most wins by a freshman and helped UNC set a school record with its 58th win.
North Carolina tacked on an insurance run in the top half of the seventh when Bolt drove in a run with a two-out RBI single to left field.
The Holberton-Bolt angle started in April when Holberton assumed the cleanup role after Bolt broke his foot against Virginia Tech. They switched back once Bolt returned in mid-May, but the rookie left fielder has struggled to regain his early season form, batting .211 with nine RBIs and three extra-base hits in 17 games entering Tuesday's contest.
In addition to his RBI single, Bolt (2-4, RBI) also blasted a double to the warning track in right field in the fifth, giving him his third two-hit outing in six games.
"I just really reverted back to what got me here, and that was staying tall and taking what the pitcher was giving me instead of trying to drive some extra base hits there in the 4-hole and trying to move some guys around with runners at either first or second in scoring position," Bolt said.
Fox said he discussed the lineup change with hitting coach Scott Jackson, noting that it was more for just a change and not as an indictment of Bolt's recent play. The move also gave UNC back-to-back right-handed hitters to match LSU's swarm of southpaws.
Thornton's ability to pitch into the eighth allowed for UNC to insert its other trusted reliever, Chris McCue, in for the save opportunity. After working out of a bases loaded jam in the eighth, the sophomore right-hander handled the heart of LSU's lineup in the ninth to secure his second save of the season.
North Carolina will play its next elimination game against the UCLA/N.C State loser on Thursday night at 8pm ET.