Matheny charged out of the dugout to argue the safe call - a rarity in spring games.
Jaime Garcia cruised through the first 5 2-3 innings for St. Louis, allowing only four hits. Danny Espinoza finally put the Nationals on the board with an opposite-field home run that sailed over the wall in right.
Washington starter Gio Gonzalez put two tough outings behind him by allowing one run on three hits and a walk while striking out seven in five innings. He retired the Cardinals in order the first time through the line-up.
The Cardinals finish spring training with a 16-9-2 record. They will travel to Springfield, Mo., to scrimmage against their Double-A affiliate Monday before returning to Florida to open the season against Miami on Wednesday.
Washington (12-15-3) still has two more spring training games remaining, both against Boston.
Link to boxscore: Washington 2 at St. Louis 1