Miguel Cabrera hit his 15th homer of the season for Detroit. He flied out to the right-field wall with a runner on to end the game as Pittsburgh beat the Tigers for the second straight night.
Sanchez cruised through the first six innings, surrendering only a solo home run to Neil Walker. Things unraveled in the seventh as the Pirates batted around.
Sanchez tossed his fourth career one-hitter in his previous start, an easy 6-0 romp over Minnesota last week. He kept rolling early against the Pirates, who have struggled to score when Burnett starts.
Walker — whose solo home run in the 11th inning produced the only run in a 1-0 Pittsburgh victory in Detroit on Tuesday night — provided the only two hits off Sanchez through the first six innings.
Sanchez retired 16 of 17 batters at one point and appeared to have all the cushion he needed when Andy Dirks doubled home Don Kelly with one out in the fifth and Cabrera followed two batters later by poking a 92 mph fastball from Burnett into the seats in right field, giving the Tigers a 3-1 lead.
Andrew McCutchen lined out to start the bottom of the seventh when suddenly Sanchez's command disappeared.
Garrett Jones singled and Russell Martin walked on four pitches. Alvarez followed by driving a ball to the wall in left-center, scoring both runners. Snider took the next pitch and hit it off the wall in right with Alvarez just beating the relay throw to put Pittsburgh in front.