Diaz signed a minor-league contract with the Astros on Friday, Chandler Rome of The Athletic reports.
Diaz elected free agency Thursday after being DFA'd by Houston on Monday, and he will now return to the Astros organization after exploring his options on the open market. The 29-year-old righty will report to Triple-A Sugar Land, after posting a 5.05 ERA and 1.40 WHIP in 2023 at that level as part of the Tigers' farm system.