Arizona sophomore guard Allonzo Trier hasn’t played a game yet this season, and the reason for his absence, as first reported by ESPN’s Jeff Goodman and later confirmed by a statement from Trier, is a failed drug test in September.

Trier was initially suspended by the NCAA for the entire 2016/17 season after testing positive for performance-enhancing drugs during the preseason, but appealed the decision, won the appeal in December, and has been cleared to return to action once the drug completely exits his system.

Trier said in the statement that he was “shocked” by the initial positive test.

“I have never knowingly taken a banned substance,” Trier said. “After finding out that I was given a banned substance by a well-intentioned, but misguided person not associated with the University after an injury, I presented this information to the NCAA. The NCAA agreed that I had no knowledge of receiving the substance and my eligibility was restored.”

Trier has been practicing and traveling with the Wildcats since winning the appeal, but the drug remained in his system at the last time of testing. Trier said he is unsure of when the substance will be completely out of his body.

Trier, a 6-foot-5 wing, was expected to be one of Arizona’s stars this season after averaging 14.8 points and 3.3 rebounds per game as a freshman. He was the Wildcats’ leading returning scorer. Others have stepped up in his absence, though, and Arizona is 16-2 and 5-0 in the Pac-12 heading into road games this week at USC and UCLA.

Arizona coach Sean Miller addressed Trier’s absence Monday on the College Hoops Today podcast, telling host Jon Rothstein, “Allonzo’s situation is kind of a once-in-a-lifetime situation. He practices every day, so you have a great feel for how good he is, and in my mind, he would be one of the best guards in college basketball this season.

“I can’t even say I’m optimistic right now,” Miller said. “You learn in crisis to only focus on the things you can control. This is a once-in-a-generation type deal. I really have no feel on what’s going to happen.”

It remains unclear when or if Trier will play for Arizona at all this season.

Here is Trier’s full statement: