And they said there'd be no math

SAN FRANCISCO -- With half the matches on the back nine, here's what we know:

We know the U.S. leads in six matches, and the Internationals in the other six.

We know that if those leads hold, the U.S. would have 18.5 points, which would secure their third-straight Presidents Cup.

We know that in match play, leads never hold long.

We know that if the Internationals were to come back, they would need two of the matches they currently trail in to turn in their favor. We know that score-wise, their best chances of a reversal lie with  Retief Goosen, who is currently 1 down to Phil Mickelson, and Camilo Villegas, who is 1 down to Hunter Mahan.

In other words, we know that things are not looking good for the International team.

-- Sam Weinman