SALT LAKE CITY - Gonzaga needed last-minute heroics to survive its NCAA Tournament opener the last time it drew a No. 1 seed. For a half, it looked like the Bulldogs were headed for a repeat of history.

This time, top-seeded Gonzaga did not let an inspired underdog hang around. The Bulldogs clamped down on defense and raced away from South Dakota State in the second half for a 66-46 first-round NCAA Tourament victory on Thursday.

Gonzaga (33-1) trailed much of the first half, but pulled away after halftime by holding the Jackrabbits to 29.0 percent shooting in the second half. The Bulldogs forced 13 turnovers and held South Dakota State (18-17) without a field goal for long stretches.

"We were able to grind out a tough game, not a pretty game," Gonzaga guard Nigel Williams-Goss said. "It feels good when you win a game when you know you didn't play your best."

Jordan Mathews scored 16 points and Johnathan Williams collected 14 rebounds to lead top seeded Gonzaga

Mike Daum, who entered the game as the nation's second-leading scorer at 25.2 points per game, scored 17 points to lead South Dakota State. The Jackrabbits trailed the entire second half.

"Our guys guys showed up here and competed from start to finish," Jackrabbits coach T.J. Otzelberger said. "Gonzaga is an outstanding basketball team. We have tremendous respect for them. They did a really good job. They're a really good team."

After struggling on offense before halftime, Gonzaga blew the game wide open early in the second half. Williams-Goss buried back-to-back jumpers to give the Bulldogs their first double-digit lead at 37-26. South Dakota State cut it to 40-33 on a jumper from Daum with 13:59 remaining before Gonzaga buried the Jackrabbits for good.

The Bulldogs allowed just three points over a nine-minute stretch and steadily pulled away. Williams-Goss capped the 16-3 run with another jumper, giving Gonzaga a 56-36 lead with 5:00 left.

"We had to dig really deep to show our toughness to dig through that thing and we definitely did that," Bulldogs coach Mark Few said. "Our defense carried us this entire game, which, you know, it has a lot this year - more than people realize."

Gonzaga shot just 31.0 percent from the field in the first half. The Bulldogs did not take their first lead until Zach Collins made a layup with 1:40 left before halftime. That go-ahead basket from Collins highlighted a 7-0 run over the final 2 1/2 minutes of the half that gave Gonzaga a 26-22 lead going into the locker room.

South Dakota State made three of four shots to open up an 8-2 lead. Gonzaga rallied and tied it at 12-12 on a 3-pointer from Collins.

The Bulldogs could not overtake the Jackrabbits when both teams went through a four-minute drought without a field goal. They combined to miss 14 shots in that stretch. Daum finally broke the ice with a 3-pointer to put South Dakota State ahead 22-19.

That ended up being the only basket for the Jackrabbits over the final 7:44 of the half. South Dakota State missed 10 of 11 shots in that span and committed three turnovers.

NOTES: Gonzaga finished with a 50-38 advantage in rebounds after South Dakota State held a 22-21 edge at halftime. ... Jackrabbits fell to 0-4 all-time in the NCAA Tournament. ... Gonzaga has won its NCAA Tournament opener nine straight seasons. ... South Dakota State shot 25 percent from 3-point range in both halves.