WASHINGTON (AP) — A Washington homestand that began with three losses to Atlanta was about to culminate in a six-game winning streak and the Nationals at .500 for the first time since mid-July.One swing of the bat rewrote that happy ending.Pinch-hitter Hector Sanchez hit a three-run homer with two outs in the ninth inning and the San Francisco Giants beat the Nationals 4-3.Down to his last strike, Sanchez connected off closer Rafael Soriano (2-3) on a 3-2 pitch. The drive landed just inside the right field foul pole in the second deck.“That one hurt. That one hurt,” Washington manager Davey Johnson said.The loss kept the Nationals (59-61) from reaching .500 for the first time since July 20.Ian Desmond doubled home two runs and Jayson Werth added two hits for the Nationals.Buster Posey led off the ninth with a single against Soriano and Roger Kieschnick drew a two-out walk.