Thomson split a pair of Class AAA games -- winning 4-0 over Walnut Grove in the first game. The Bulldogs lost 16-1 to White County, which hit five homers.
Greenbrier (31-10) will play Jones County at 7:30 tonight. The winner of that game will move into the championship game on Saturday.
Thomson (22-10) will play in an elimination game today at 1 p.m.
The Wolfpack, which had to go nine innings in both wins, defeated Loganville 1-0 in the first game and Union Grove 2-1 in the second game.
"The 'Cardiac 'Pack' was able to survive," Greenbrier coach Garrett Black said. "The kids are fighting so hard. These kids just don't quit. I'm so proud of them."
Savannah Coon picked up the win in both games for Greenbrier.
Thomson's Khedeja Fanning hit a solo homer to lead the Bulldogs to a victory in the first game.