Entering the week, Day was “optimistic” he could make it through the event after withdrawing from the BMW Championship two weeks ago with the same affliction. Pundits have eyed his violent downswing as a probable cause for his back issues.

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Day was 3 under for the tournament, just three shots behind the leaders, when he chose to withdraw. The injury seemingly came on the eighth hole when he chose to hit a driver out of the rough.

It remains to be seen when Day will tee up next, but it’s plausible he could be done for 2016, thus making his next start at the 2017 opener in Hawaii.

Day, 28, is the No. 1 golfer in the world, but Dustin Johnson is in contention this week and could overtake him soon.