Twice major winner Jordan Spieth said Wednesday he is still undecided about whether to participate in August's Rio Olympic Games or opt out because of the Zika virus like several of his fellow professionals.

The American world No.2 is the highest-ranked golfer left in the field after No.1 ­Jason Day withdrew Tuesday, citing concerns over Zika.

Golf is returning to the Olympic Games for the first time since 1904, but the Games has already been hit by several high-profile withdrawals.