Dunn (ankle) has been ruled out for Friday's game against the Mavericks, Evan Sidery of Forbes.com reports.
The 21-year-old was considered doubtful for Friday's contest after suffering an ankle sprain Wednesday against Miami, so it's not a surprise he won't be available in Dallas. Dunn's next chance to take the court will come Sunday versus the Kings, but he could miss more time given the recency of the injury.