MLB has announced home field advantage for the Wild Card game will be decided by the head-to-head records of the two teams, not who has the best overall record. If the season series is tied, the second tiebreaker will be best record within the team's division.
If the season ended today, the NL Wild Card game would be the Braves vs. Pirates; the AL Wild Card game would be the Orioles vs. Tigers.
The Braves and Pirates split a four-game series in April. They finish the season against each other with a three-game series in Pittsburgh from October 1-3 that could have major implications on the Wild Card game.
The Tigers took two of three from the Orioles in a series in Baltimore immediately following the All-Star Break. The two clubs meet up again for a three-game series in Detroit from August 17-19.