The American entered the week as the fifth seed but should he go one better than last year's defeat in the final, he will replace Jon Rahm at the top of the Official World Golf Ranking.
A favourite among the local crowds due to his days at the University of Texas, Scheffler has proved himself to be an excellent match play operator, getting all the way to the final here last season and then winning 2½ points in the United States' record Ryder Cup victory.
With two wins from six starts in 2022, the 25-year-old is arguably the form player in the world but he refused to get carried away by the prospect of being World Number One.
"I wouldn't say I'm in a rush really to do anything out here," he said. "I'm pretty blessed to be playing out here on the PGA Tour. I'm just enjoying myself out here and trying to do the best I can and to compete."
He added: "I played really solid this afternoon. I didn't really give Seamus many openings outside of one. I just really kept the pressure on him this afternoon."
Scheffler put an approach inside four feet at the fifth and then eagled the par-five sixth from six feet to go 2 Up but Power was level at the turn as Scheffler bogeyed the eighth and the man from Waterford birdied the ninth from six feet.
A two-putt birdie on the 12th and an approach to ten feet at the next then put Scheffler 2 Up again before he chipped in for eagle on the 16th to secure victory.
Johnson won this event with a perfect record of seven wins in 2017 and will be looking to do the same again after making it ten match play wins in a row dating back to the Ryder Cup - where he was also undefeated.
"I know Scottie," he said. "I've played with him quite a few times and then he was on the Ryder Cup team with us. He's a good competitor, and it's going to be a tough match.
"It was a long day but I felt like I played really well all day."
Koepka chipped in for birdie on the second and put his approach to nine feet on the third to go 2 Up and while a ragged tee-shot handed Johnson the fifth, Koepka won the sixth.
That would be the last hole he won, however, as Johnson holed from 13 feet on the seventh and 11th for birdies and made a 30-footer on the 15th before driving the green on the par-four 18th for another gain.
Kisner has a remarkable record at this event, with 21 wins from 28 matches at Austin Country Club since 2016.
"I might be playing better now than I did in 2019, just from an overall whole game standpoint," he said. "The ball-striking has not been as sharp as I wanted the last couple of days but I'm also on a four-week stretch here where I've played a lot of golf.
"I really love being in contention on Sunday in a stroke play event. If I'm teeing off in 30th it's hard for me to get really into it. Out here it feels like Sunday every day, which is a lot of fun."
Zalatoris bogeyed the first and Kisner produced a remarkable shot on the third, using the contours around the green to put his approach inside two feet.
Zalatoris won the fifth with a birdie but he also bogeyed the fourth and ninth to leave Kisner 3 Up at the turn.
Kisner then holed a 39-footer at the 11th and birdied the par-five 12th to go 5 Up, with Zalatoris' win at the next only delaying the inevitable.
Conners lost all three of his matches on debut at this event last year but has won them all this year - including a Paul Casey concession due to back problems - as he becomes the first Canadian to make the semi-finals.
"I feel great to be in this position," he said. "Feel like I've played really well. Some hard-fought matches, had to earn it, nothing was really given to me. It feels great to be sitting here.
"Still feeling energised. I think I'll have some adrenaline tomorrow and that'll help me get through."
Ancer trailed for the first time all week on his 70th hole when Connors left himself five feet for birdie at the fifth and he also birdied the par-five next, with the Mexican hitting back from 13 feet at the eighth.
A tee-shot to similar range at the par-three 11th evened things up but Conners led again with a birdie from 15 feet on the 14th.
A two-putt birdie from the fringe on the par-five 16th then put Conners 2 Up with two to play but Ancer took the match up the last as he got up and down after missing the green at the 17th before Conners took the last.