The 22-year-old is the first Pirates player since 1955 -- and only the third ever -- to hit safely in his first seven games.
In 1955, Roberto Clemente went 11-for-30 in his first seven big league games. With that third-inning single, Polanco was 13-for-33.
In Wednesday night's game, Polanco can separate himself from Buccos history by becoming the first player to debut with hits in his first eight games.
"I know about that," Polanco said following the game, a 6-5 Pirates loss, "but I don't think about it at all. I can't. All I can do is keep going out there and continue playing the way I have."
In his eighth game, Clemente went 0-for-4 against Cincinnati.
Zip Collins, the only other Pittsburgh rookie to collect hits in his first seven games, in 1914, also went 0-for-4 in No. 8, against the Braves.
Tom Singer is a reporter for MLB.com and writes an MLBlog Change for a Nickel. He can also be found on Twitter @Tom_Singer. This story was not subject to the approval of Major League Baseball or its clubs.