In the fourth Ashes Test match, Usman Khawaja was left out of the Australian squad. The decision came as a result of several factors:

1. Steve Smith’s Return: After recovering from a concussion, Steve Smith made a comeback for the fourth Test. His inclusion meant that Usman Khawaja had to make way for him in the batting order.
2. Marnus Labuschagne’s Performance: Marnus Labuschagne had impressed during Smith’s absence and cemented his place in the side. His consistent performances influenced the selectors to retain him in the playing XI.

As a result, Khawaja missed out on the fourth Ashes Test, and Steve Smith took his place in the lineup.