Atkins and NFL Hall of Famer Anthony Munoz are both headlining the free "Road to Victory Concert" in Springfield, Ohio, on Thursday night. But ahead of that event, Portman tweeted that he and Atkins were taking in a Cincinnati Reds game.
The two posed for a photo with Reds first-base coach Billy Hatcher.
The Reds played the Milwaukee Brewers in a home game on Thursday afternoon.
Atkins also headlined a welcome party for the Republican National Convention in Tampa, Fla., last month.