Diaz spent the offseason gaining a better understanding of his delivery in an effort to reduce the mechanical issues that hampered him last season, Ryan Divish of the Seattle Times reports.
A breakout 2016 campaign had the young reliever primed to be Seattle's closer heading into the 2017. However, first-half struggles and control problems led to him being demoted from ninth-inning duties for a portion of the season. He still finished with 34 saves and a respectable 3.27 ERA, but Diaz wants to prove he's for real this season. After the tumultuous 2017 campaign, he came into camp with some throwing sessions already under his belt and a new mentality on the mound. During an early bullpen session, Diaz noted "when I missed a couple pitches, I refocused my mind and made the adjustment." Diaz is lined up to be the Mariners' closer once again, and if he can make quick adjustments like this during the regular season, he could be even more dominant in his second full big-league season.