Eugenio Suarez played shortstop against the Cardinals this past Thursday. Shortstop lost. 

Suarez is an excellent power hitter. His 98 homers the past three years entering this season is proof of that. What Suarez isn't is a slick fielder. The Reds have him playing shortstop this season after he's played third base for the past five seasons. 
Shortstop is not a position you can get away with a bad fielder. The Cardinals, aided by two errors from Suarez, drilled the Reds and Luis Castillo, 11-6, in the series opener on  Thursday.  

Now the Reds drop down in pitching class from Castillo to Tyler Mahle, who only is this high in the rotation because Sonny Gray is out with back spasms. I have my doubts if Mahle is even backend rotation material. He certainly doesn't figure to get much defensive help from the left side of his infield. Mahle is 1-3 with a 5.45 ERA in eight career starts against St. Louis. 

Adam Wainwright will be going for the Cardinals. Wainwright is 39 and well past his prime. But he's still crafty. Wainwright made 10 starts in 2020 and has his finest season in five years with a 3.15 ERA. Wainwright pitched well in spring training, too, with a 2.42 ERA in six games.
Maybe Wainwright will show his advanced age as the season progresses, but right now he's fresh and I like him better than Mahle. So getting the Cardinals as an underdog is a value play in my book.