Diaz fired two scoreless innings in Wednesday's 5-3 extra-inning loss to the Astros, giving up a hit and a walk while also recording two strikeouts.
The Mariners closer came on for the ninth and 10th innings, successfully preserving a 2-2 tie. The outing was Diaz's first of the season, as the Mariners had trailed in the late innings in the first two games of the series. The 23-year-old will be counted on to build on his impressive 18-save 2016 major-league debut, but with Seattle's offense generating a total of four runs in the first three games of the season, he's yet to have the opportunity.