A fantastic approach by Watson at the seventh hole saw him tap in for a birdie to put the Americans two up as they approached the turn.
America were already three up by the time Simpson nudged a birdie putt in at the 13th, putting the home side four up with five to play.
Watson missed an eagle putt at the 14th that was for the match, but he stopped it right next to the hole.
That meant that either Molinari or Rose had to sink theirs to extend the match, but neither could find the bottom of the cup and USA extended their overall lead to 9-4.
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