Diaz will transition into a relief pitcher, Jason Churchill of Prospect Insider reports.
Diaz is widely considered to be Seattle's top prospect, but even then, he wasn't expected to be the club's future ace while spending the past four seasons working his way up the farm system. The ability to reach high-90s with his fastball certainly suggests a role as a closer could work out just fine, but he's still not in line to join the Mariners until the 2017 season.