Barnes also had a couple of critical kills in the deciding fifth set as she sent well-placed shots down the line from her left-side outside hitting position.
"My teammates just kept saying [it was open]," Barnes said. "We just keep talking to each other and everyone who hits. We just keep telling them which spot to hit. That's part of playing as a team is communication, and that's what helped us."
Skyline, led by the hitting of senior Kassie Sorenson and sophomore Abby Selcho, jumped to wins in each of the first two sets. In the third set, however, a 15-14 Mustangs' advantage turned into a seven-point lead following a 7-1 stretch where senior middle Marisa Perrett got a kill and a block.
After winning the third and fourth sets, Mountain Crest briefly relinquished control of momentum when Skyline raced to a 6-1 lead in the fifth.
The multi-dimensional Mustangs' offensive attack ultimately was aided in the final set by Eagles serving errors.
"You give them a third of their points in missed serves, and you're probably not going to win," Skyline coach Jami Hutchins said. "We told the kids after Game 1 that this is not the Mountain Crest we knew from playing them earlier in the year. They're a great team and they came at us in Games 3, 4 and 5."
Mountain Crest reached the quarterfinals by winning another five-set thriller 25-21, 21-25, 14-25, 25-16, 15-11 over Bountiful.
Bountiful had finished second in regular-season region play, while Skyline won its region. Mountain Crest, meanwhile, finished third in Region 7.
"I always thought we still had a shot at it," said Mountain Crest coach Lori Karaghouli, whose squad will take on Timpview, a 25-14, 25-15, 25-15 quarterfinal victor over Judge Memorial. "I was proud the way we came back in the third game. This team is full of true competitors, and they really wanted to win."
Class 4A state tournament
Saturday at Utah Valley University's UCCU Center
10:30 a.m. • Sky View vs. Woods Cross
12:30 p.m. • Mountain Crest vs. Timpview
5:30 p.m. • Semifinal winners