St. Louis' Yadier Molina (857,109 votes), Washington's Matt Wieters (573,072) and Los Angeles' Yasmani Grandal (525,432) complete the top five in voting.
Posey, the lone Giant to appear among the top five vote recipients at any position, also was elected by fans to start in 2012.
Fans may cast votes for starters at MLB.com and all 30 club sites -- on computers, tablets and smartphones -- exclusively online using the 2017 Esurance MLB All-Star Game Ballot until Thursday, June 29, at 11:59 p.m. ET. On smartphones and tablets, fans can also access the ballot via the MLB.