The Cowboys didn't shoot it well, either, finishing at 40.4 percent from the field. Any hopes at a rally were foiled by a 29.4 percent effort after intermission.
And from the foul line, OSU went 8-for-15, with three misses coming on the front end of 1-and-1 opportunities.
“It felt like everything that could go wrong, went wrong,” Smart said. “And you can't have games like that, especially at this time, in the NCAA Tournament. You're supposed to get those games out of the way.
“And unfortunately, we had one of those games tonight.”
Markel Brown led the Cowboys with 16 points in defeat. Smart added 14, but struggled shooting, making just 5 of 13 field-goal tries and 4 of 8 free throws.
Damyean Dotson led the Ducks with 17 points and Arsalan Kazemi grabbed 17 rebounds, keying Oregon's domination on the boards.
The Cowboys never posed a serious threat in the second half, failing to cut the lead to single digits at any time.
OSU's season ends at 24-9, with highlights for sure, yet a final lowlight that won't be easy to shake.
“It's extremely tough,” said Cowboys forward Michael Cobbins. “We had a great team here. We had a great season. And we all wanted to continue going on this journey and making the best of it. So it's extremely tough getting cut short like this.
“But this is just fuel for next year.”