With the Cougars' 19-point lead down to six early in the second half, Mika ran down Kyle Tresnak and blocked his shot as the Wildcats tried to finish a fast break.
Not only did Mika's rejection prevent Weber from cutting BYU's game-long lead to 46-42, it triggered a 15-1 run. In the end, that was the decisive 41/2-minute stretch of the game.
"I remember the block," said Mika, who became the first true freshman to start an opener for BYU since Mark Bigelow in 1998.
"I saw [Tresnak] leaking out, and I knew that if he scored that would be a big momentum-changer. So I went and got it."
Weber State coach Randy Rahe thought the block was pivotal in the outcome.
"If [we] make that shot," he said, "you never know what's going to happen. But Mika made a hell of a play. He chased it, he played with great effort and made a hell of a play."
Tyler Haws led BYU with 28 points and Matt Carlino added 22. In 24 minutes, Mika finished with seven points, five rebounds and three blocks.
For Weber State, Tresnak was outstanding. He scored 24 points and kept the Wildcats close in the opening minutes. Wildcat star Davion Berry ended up with 23 points, but he didn't score his first field goal until 4:40 remained in the first half. By that time, BYU owned a 38-22 lead.
Rahe attributed Weber's slow start to some nervousness, which caused the Wildcats to "miss point-blank shots. ... We just could not score."
BYU owned a 44-33 lead at halftime, but the Wildcats never went away, even after Mika's block and BYU's big run early in the second half.
"We dug ourselves such a hole," Rahe said, "and it's so hard to come back on a team like this especially when you dig that hole on their court.
"But I was really proud of our kids. I thought we fought. We stayed together. I thought we showed some signs that we have a chance to be a pretty good basketball team."
Haws thought so, too.
"You have to give Weber State credit," he said. "They made plays and they have players that can make big shots. It felt like we'd get to 15 and just couldn't get over that hump. But they hit some big-time 3s and kept battling for 40 mnutes. So it's a good win for us."
O Tyler Haws scores 28 points for BYU against Weber State in the season opener for both teams.
• BYU jumps to a 17-3 lead in the first seven minutes and holds off the Wildcats in the second half.
• Kyle Tresnak leads Weber State with 24 points, and teammate Davion Berry adds 23.
BYU 81, Weber State 72
WEBER STATE (0-1)
Richardson 0-4 0-0 0, Berry 8-16 4-5 23, Bolomboy 4-12 3-6 11, Senglin 4-11 3-4 14, Tresnak 10-16 4-4 24, Gittens 0-1 0-2 0, Williams 0-3 0-0 0, Hill 0-3 0-0 0.
Totals 26-66 14-21 72
Mika 3-6 1-2 7, Carlino 10-22 1-1 22, Haws 9-21 9-12 28, Collinsworth 4-9 3-4 11, Austin 1-2 0-0 2, Sharp 0-1 0-0 0, Winder 2-5 0-0 5, Halford 1-2 0-0 2, Bartley IV 1-2 0-1 2, Worthington 1-2 0-0 2.
Totals 32-72 14-20 81
HalftimeBYU 44-33. 3-Point GoalsWeber St. 6-18 (Senglin 3-5, Berry 3-6, Hill 0-1, Williams 0-2, Richardson 0-4), BYU 3-9 (Haws 1-2, Winder 1-2, Carlino 1-4, Halford 0-1). Fouled OutNone. ReboundsWeber St. 40 (Bolomboy 13), BYU 46 (Haws 13). AssistsWeber St. 9 (Richardson 3), BYU 18 (Carlino, Collinsworth 6). Total FoulsWeber St. 17, BYU 20. TechnicalBolomboy. A15,696.