Dunn will undergo surgery on his right elbow Monday, C. Trent Rosecrans of The Athletic reports.
Dunn has been on the shelf since late June due to a right elbow sprain, and he suffered a setback last week shortly before he was scheduled to begin a rehab assignment. The Reds haven't given an updated timeline for the 27-year-old's return, though his procedure will almost certainly rule him out for the remainder of the season. Dane Myers figures to continue working as Cincinnati's primary center fielder while ceding an occasional start to TJ Friedl.