Castle appears to be locked into a starting role at shooting guard, per Jared Weiss of the New York Times.
There's some discourse surrounding whether or not Dylan Harper should start over veteran De'Aaron Fox in 2026-27, but Castle seems to be safe from that debate. Castle was instrumental to the Spurs' deep playoff run last year, averaging 18.2 points, 6.1 assists, 5.0 rebounds, 0.9 steals and 1.5 three-pointers per game across 23 postseason appearances.