For a team ranked outside the nation’s top 10 and focused more on winning a conference title than a BCS crystal football, there is no such thing as a must-win, nonconference game in September.But for the Texas Longhorns, Saturday’s 6 p.m. contest at Brigham Young comes close. It stands as a referendum on the off-season switch to an up-tempo offense designed to benefit quarterback David Ash and help an inconsistent defense become more comfortable facing the spread offenses that dominate the Big 12. It offers a hostile environment against a strong defensive team to gauge the mental toughness of a Texas squad that has lacked that commodity in recent seasons.Most important, it marks the start of a three-week September stretch in which No. 15 Texas (1-0) will face increasingly tougher tests to determine how much is on the line when the Longhorns meet No. 16 Oklahoma (1-0), Oct. 12 in Dallas.Based on this week’s college football polls, the OU game will be Texas’ first encounter with a Top 25 opponent. But Texas’ march through BYU, Ole Miss and Kansas State marks a significant stretch for a team with a combined 22-16 record since the 2009 season. The Longhorns have a history of struggling against BYU (1-2 in career matchups) and K-State (five consecutive losses in the series). Ole Miss (1-0), a bowl team last season, appeared much-improved in its season-opening victory over Vanderbilt. The September statement games will decide whether Texas is a contender or pretender in the Big 12 race.One loss during this September stretch, particularly on the front end against BYU, could erase whatever feel-good mojo permeates the locker room after last week’s 56-7 rout of outmanned New Mexico State. And Texas cannot afford to have its momentum turned in the wrong direction this early in a season when coach Mack Brown needs to deliver a Big 12 title or BCS bowl berth to prove the program is “fixed,” as he declared at the start of fall drills.Brown acknowledged the significance of the BYU-Ole Miss stretch heading into the team’s Sept. 21 matchup against Kansas State, the defending Big 12 co-champs.“Both of these teams are as good as we are. Our guys know that,” Brown said. “This is great for us to be challenged. We get the tough road trip, which we need. We get the tough SEC game, which we need going into our Big 12 opener.”Clearly, Brown believes the Longhorns — who rolled for a school-record 715 yards against New Mexico State — are capable of meeting the challenge. So does cornerback Quandre Diggs, who declared this a better team than the inconsistent squads of the past three seasons.“There’s something different about this team,” Diggs said. “If we go out focused and do what we’re supposed to do, I think we can win every game.”Maybe. But let’s tap the brakes on runaway optimism, at least until the final gun sounds Sept. 21 against K-State. Texas still has plenty of unanswered questions and had too many turnovers (3) in its opener. The Longhorns trailed one of college football’s cellar dwellers, 7-0, after 28 minutes of action in Austin.But the final 32 minutes were total domination, underscoring the potential for this team to wear down opponents with its up-tempo attack and defensive depth. The unanswered question, at this point, is whether Texas can do that to better teams.The key to answering that question is Ash, who rebounded from two first-half interceptions to finish with 434 yards of total offense. He accounted for five touchdowns (four passing, one rushing).And he’s got an even larger spotlight on him Saturday, along with Brown, thanks to Monday’s magical debut by Florida State freshman quarterback Jameis Winston. After a near-flawless debut in a 41-13 rout of Pittsburgh (25-of-27, 356 yards, 4 TDs), Winston mentioned that he wanted to go to Texas but was not recruited.In a Wednesday news conference, Brown said Texas coaches were “told by people we trust” that Winston, who played high school football in Alabama, was a lock to sign with FSU or Alabama. After in-state whiffs on Robert Griffin III and Johnny Manziel, Brown’s recent track record in pursuing high-caliber quarterbacks has come into question.Ash, a junior, could make that a moot point with a breakthrough season after two years of inconsistent efforts. Some signs surfaced Saturday.“He’s been questioned about his ability to come back from mistakes and he did that,” Brown said. “He was as good as I’ve ever seen him as far as making a play and thinking he should. Or making a bad play and moving on. He did very well at both.” The best part? Ash was far from satisfied.“I feel like I have a lot to improve,” Ash said. “I made some mistakes that didn’t need to happen.”Now, he must avoid them against BYU if the Longhorns are to win their first statement game in a September filled with them.