Mills missed his opening four shots then connected on six three-pointers over the next nine minutes before injuring his wrist after heavy contact led to a fall in the paint.
Doctors will evaluate Mills condition in advance of St. Mary's next game against Portland on Sunday at 1:00pm AEDT.
"He fell on his wrist and I'm not sure if it's his finger that may be broken or his wrist but his arm swelled up a little bit so we sat him as a precaution in the second half," Gaels assistant coach David Patrick said.
"He was having trouble passing the ball and shooting it and hopefully he'll be ready for Portland. I'm not sure but if I was a betting man I'd probably say no, he won't play, let him get some rest."
Mills finished with a game-high 18 points on 6-of-8 three-point shooting in just 17 minutes on court, extending his double-figure-scoring streak for the Gaels to 24 games dating back to his freshman season.
The Gaels lead 39-33 at half time today but with Mills sitting out the rest of the game Gonzaga steamrolled its mid-major archrival with a 36-23 second half. With a proliferation of professional scouts in attendance and a massive national television audience in America following the game, the pressure was on Australia's brightest young guard to produce a performance worthy of the attention he is receiving - and he delivered, for a half. It was only St. Mary's second loss from twenty games this season but drops the Gaels to second in the West Coast Conference behind Gonzaga.