Posey, the 2010 NL Rookie of the Year, was behind the plate for the first two innings and he hit a flyout in his only at-bat. Sanchez, who played the entire game at designated hitter, went 1 for 4.
Posey played for the first time since May 25, 2011, when he tore ligaments in his left ankle in a home-plate collision. Sanchez hadn't played since he suffered a dislocated right shoulder on June 10.
Giants outfielder Melky Cabrera hit a two-run homer, his third of the spring. Brandon Belt also homered.
Left-hander Aroldis Chapman started for the Reds and pitched two perfect innings, striking out two. Todd Frazier homered for the Reds.