The Astros selected Diaz's contract Monday.
Diaz joined the Astros on a minor-league contract July 13 after being released by the Athletics one week prior. He'll be starting up his second stint in the big leagues with Houston, after previously appearing in 262 contests between 2019 and 2022. Before Oakland cut him loose, the 33-year-old utility man logged 30 plate appearances in the big leagues this season, slashing .103/.133/.103 with no extra-base hits.