Center Przemek Karnowski is out for the season with a back injury. Against BYU, forward Domantas Sabonis was in foul trouble the entire game and limited to five points. Forward Kyle Wiltjer tried to carry the team himself, scoring 35 points and grabbing 10 rebounds, but it wasn't enough as Gonzaga (13-4, 5-1 West Coast Conference) saw a seven-game winning streak snapped.
''Domas got into foul trouble and we had to pull him out,'' Gonzaga coach Mark Few said. ''He's a huge part of what we are.''
As a result, BYU outscored Gonzaga in the paint 40-20, and won the rebound battle 41-39.
It was the second straight year that BYU beat Gonzaga in Spokane, dealing the Zags a rare home loss in a West Coast Conference game.
BYU was having a poor game shooting, and trailed Gonzaga for much of the game.
Then the Cougars got hot late, and freshman guard Nick Emery hit a 3-pointer with 1:38 left that provided the winning points. It was his only basket of the game.
Kyle Collinsworth scored 20 points and Chase Fischer added 18 for BYU (13-5, 4-1).
''We just stayed positive and kept fighting,'' Collinsworth said.
Picking up a rare victory at Gonzaga last year - it broke the Zags' 41-game home winning streak - gave them confidence they could do it again, even as BYU spent most of the game shooting in the 30 percent range, according to Collinsworth.
The confidence extended to Emery, he said.
''Nick just stayed in the present,'' Collinsworth said. ''As soon as he had that ball he just knocked it down.''
BYU missed its first 12 3-point attempts of the game, but made three in the final 8 minutes, including the game-winner.
''Our effort and energy was there the whole game,'' Collinsworth said. ''We are playing better as the season goes on.''
Wiltjer is the leading scorer in the WCC at 21.5 points per game and has reached 20 points 11 times this season.
But he missed a free throw with 8 seconds left that would have tied the game.
''It was really disappointing,'' he said of the loss. ''We really couldn't get stops'' late in the game.
Neither team shot well from the field, with BYU hitting 41 percent and Gonzaga just 36.8 percent.
Fischer's 3-pointer, the first of the game for BYU after 12 misses, brought the Cougars within 56-54 with 8:33 left.
Wiltjer replied with a 3-pointer and a long jumper to keep the Zags ahead.
Collinsworth hit three straight baskets as BYU got within 63-61 with 3:40 left. Fischer completed a three-point play to put the Cougars ahead 64-63.
Kyle Dranginis scored on a long jumper to put Gonzaga up by one, but Fischer scored again to put BYU ahead.
After Eric McClellan hit two free throws for Gonzaga, Emery made his 3-pointer to put BYU ahead 69-67 with 1:32 left.
The BYU defense buckled down and Gonzaga could not get a clean shot. Wiltjer made one of two free throws with 8 seconds left to close the scoring and BYU's Nate Austin blocked a shot in the final seconds.
HBO is filming a reality series on this Gonzaga basketball season. The five-part series will debut Feb. 16.
BYU: Collinsworth is coming off his NCAA-record ninth career triple-double and averages 14.9 points, 7.9 rebounds and 7.4 assists per game. ... Fischer came in averaging 18.1 points and leads the WCC with 55 3-pointers. ... BYU came in averaging 88.5 points in conference play. ... Four Cougars average at least 12.8 points.
Gonzaga: Gonzaga came in shooting .457 from 3-point range in conference games. ... Gonzaga has posted a higher field goal percentage than 15 of 16 opponents. ... Wiltjer and Sabonis are both averaging more than 34 minutes per game because of Karnowski's injury.
BYU plays at Portland on Saturday.
Gonzaga hosts San Diego on Saturday.