GLENDALE, ARIZ. – South Carolina coach Frank Martin walked up to Gonzaga's 7-1, 300-pound man mountain who grabbed his face in pain lying on the baseline in the first half of Saturday's Final Four matchup.

Martin looked genuinely concerned about the opposing big man, slapped in the eye on a blocked shot. Przemek Karnowski wasn't OK at first. He left for the locker room but returned and contributed to the biggest victory in school history.

Gonzaga blew a 14-point second-half lead, but Nigel Williams-Goss' 23 points and Karnowski's clutch late baskets were enough to give the top-seeded Zags a 77-73 victory over No. 7 seed South Carolina at the University of Phoenix Stadium.

"The journey that we've been on has just been unreal," Williams-Goss said. "We just never stopped believing. We had the utmost confidence in ourselves the whole season long."

Depth was the story in the first national semifinal. The Zags (37-1) got major contributions outside of their All-America guard and starting center, while the Gamecocks came up just short with leading scorer Sindarius Thornwell quiet in the first half and late in the game.

Thornwell couldn't get open for a tying three-pointer and was fouled with 3.5 seconds left. The SEC Player of the Year was forced to miss the second of two free throws, and the Gamecocks failed to control a critical rebound.

Killian Tillie then hit two free throws with 2.2 seconds left to put Gonzaga into Monday's championship game. It will try to be the first one-loss team to win a title since North Carolina State in 1974.

Thornwell was averaging 25.8 points in four NCAA tournament games, but he went scoreless from the floor until a three-pointer with 3:03 left in the first half. He shot 4-for-12 and finished with 15 points. P.J. Dozier led South Carolina with 17 points and nine rebounds, and Chris Silva added 13 points and 13 rebounds.

"There's something powerful when you impact others," Martin said of his team. "And what these kids have done is pretty special."

The 6-5 Thornwell missed practice Thursday because of an illness. But he returned to practice Friday and made a comment to media about Gonzaga that didn't sit well with Williams-Goss.

"I guess they were making comments that we were the most nervous team in the tournament," Williams-Goss said. "We just heard everything this year."

South Carolina (26-11) had been mostly a second-half team in the tournament. It outscored Florida 44-30 in the second half in the Elite Eight on 52 percent shooting.

Thornwell scored four points in less than three minutes into the second half, but the Zags rallied behind Williams-Goss and twice took a 14-point lead. Williams-Goss flexed his muscles after scoring on a runner, and converted the three-point play that made it 65-51 with 10:55 left.

The Gamecocks locked down defensively and made another second-half surge. Silva's three-point play sparked a 16-0 run. Dozier tossed in a layup over Gonzaga's towering frontcourt of Karnowski and 7-0 Zach Collins, tying the score. And two Rakym Felder free throws gave his team a 67-65 lead with 7:06 remaining.

But Gonzaga kept cool under pressure and took control again — this time, behind Karnowski and Collins.

Collins' three-pointer and Karnowski's dunk and layup turned a one-point deficit into a 72-67 advantage two minutes later.

"People were knocking us for not playing any close games this year and not being able to execute like that," Zags coach Mark Few said. "So they deserve a lot of credit."

Collins finished with 14 points, 13 rebounds and six blocks. Karnowski, who had 13 points and five rebounds, didn't think Silva hit him intentionally on the early block. But he ended up getting him back on the scoreboard.

"I'm just so happy to be playing in the final day of the tournament," Karnowski said. "We did a great job staying together. That's what we've been doing all season. We don't have 37 wins for nothing."