He previously played in Major League Baseball (MLB) for the Washington Nationals and Arizona Diamondbacks.

[7][8] Grace made his major league debut with the Nationals on April 22, 2015, pitching a scoreless inning in relief against the St. Louis Cardinals.

[9] After an outing against the Cincinnati Reds on May 31, 2015, in which he gave up four runs without recording an out, the Nationals optioned Grace back to Syracuse.

[13] On July 14, 2017, Grace was called upon with the bases loaded and two outs in the ninth inning of a 5–0 game against the Reds, in his first appearance at Great American Ball Park since May 31, 2015, and induced a game-ending groundout to secure his first major league save.

[14] On August 30, 2019, the Nationals designated Grace for assignment after he posted a 6.36 earned run average across 46+2⁄3 innings[15] in 51 appearances during the 2019 season.