Perseverance paid off for the Golden Knights (8-4), who trailed from the beginning of the game until midway through the final period.
"We told the kids at half they were doing exactly what we want," said St. Francis co-Coach Jeff Stephens, who got a team-high 21 points from Gardea. "I think right now the kids are afraid to take the open shot because of us coaches, so we're trying to get that out of their minds."
Trailing, 48-41, less than 30 seconds into the fourth quarter, the Golden Knights found a willing shooter in Gardea, who knocked down two three-pointers in a span of a minute to pull St. Francis to within 50-47.
Sevan Zarifian then came up with a steal and fed Gardea, who converted a short look to pull the Golden Knights within one. Gardea would score the next four points, with a layup on the end of a fast break pulling the Golden Knights even at 53 with 4:00 to go.
St. Francis then took its first lead of the game, 56-55, with 3:22 to play when Gardea converted all three free throws after being fouled in the act of shooting behind the arc.
"When Zack is on fire, you just can't stop him," Castaneda said. "Mark Keppel was denying me the whole game and that's what allowed Zack to just have open looks."
But Keppel (8-4) got a break on a St. Francis turnover with 2:10 left and cashed in with a basket to go back up, 59-56, with 1:50 left.
Castaneda got St. Francis back within 59-58 on a layup before a steal in the backcourt by Sean Brennan went straight to Castaneda, who didn't hesitate to pull up behind the line and let it fly.
"He's better at threes than he is at twos," Stephens said.
St. Francis, which got 10 points and six rebounds from Ben Maynard, will play Muir or Maranatha in a semifinal game at 7:30 p.m. today at La Salle.