"I'm truly disappointed to announce that I won't be able to play," Day said in a statement. "I have a double ear infection and the flu, which precludes me from preparing for and playing in the tournament. I have heard great things about the Mexico Championship and the golf course. I want to thank the Salinas family for their support of the event. I look forward to teeing it up there next year."
Day is the only player among the Official World Golf Ranking top 50 expected to miss next week's event, which was held for years at Trump National Doral before moving to Mexico City.
Day sat out last fall following the Tour Championship because of a lingering back injury, returning to action last month. He made three cuts in four starts, highlighted by a T-5 finish at the AT&T Pebble Beach Pro-Am. Last week, the Aussie finished T-64 at the Genesis Open and watched his 47-week reign atop the Official World Golf Rankings come to an end.