Diaz fired a scoreless ninth inning in Sunday's 5-0 win over the Red Sox, recording two strikeouts.
The 23-year-old right-hander fired 13 of 17 pitches for strikes while setting down Dustin Pedroia, Andrew Benintendi and Hanley Ramirez. He impressively worked around throwing errors by Kyle Seager and Jean Segura that saddled him with a pair of baserunners, posting his fourth straight scoreless outing in the process. Diaz has regained the closer's role for the time being, and he should be able to easily hold on to it if he continues to turn in the caliber of performances he's recently mustered.