The NCAA ruled then that Trier would be eligible to play again once he passed a drug test. Trier was tested every 7-10 days during that time.
He scored a team-high 21 points when Arizona beat Oregon State 62-53 on January 11 in Tucson and is shooting 56.3 percent from the field over his last 10 games since playing the Beavers.
The NCAA has ruled him ineligible for competition because a January drug test showed the reappearance of a trace amount of a banned substance the organization had acknowledged he unknowingly ingested in 2016.
Arizona will appeal the decision but for now it appears that UA's chances of making it to the Final Four in April have taken a giant hit. He's put in an even more impressive performance this season, averaging 19.6 points, 3.2 rebounds, and 3.2 assists per game.
Trier previously tested positive for the same substance. Trier is also among the Pac-12's leaders in field-goal, free-throw and 3-point percentage.
It is not known whether or not Trier will be able to return to the court this season.
According to Arizona, the test returned a quantity of the substance that was "minuscule by scientific standards" and was actually left over from his previous positive performance-enhancing drug test. Trier was suspended in fall 2016 after testing positive for a PED, which he was reportedly given unknowingly following a auto crash the previous summer.
"The results of that test, confirmed today, revealed the reappearance of a trace amount of a banned substance", the UA said.
The university is appealing the ruling and is hoping he will have his eligibility restored.
No. 14 Arizona (21-6) has struggled to reach its expectations all season and is now projected to be a No. 4 seed in next month's NCAA Tournament.