The Gophers remain shorthanded at cornerback heading into Saturday's game at Penn State, with KiAnte Hardin and Ray Buford still suspended, and freshman Coney Durr out because of an unspecified injury.
Hardin started the season opener against Oregon State, opposite Jalen Myrick. Buford and Dunn are top reserves.
Myrick and Antonio Shenault have started the past two games, with Zo Craighton getting playing time off the bench.
Coach Tracy Claeys said Tuesday that the staff still is considering pulling a potential redshirt from another top freshman cornerback, Kiondre Thomas.
The Gophers ranked 11th in the nation in pass defense last year (179.5 yards allowed per game). With Eric Murray (Chiefs) and Briean Boddy-Calhoun (Browns) in the NFL, the Gophers rank 68th (228.7) in pass defense so far this year.
"I mean, we're battling," defensive coordinator Jay Sawvel said. "We've got one guy who was probably one of our better ones in camp that's out, in Coney, and you've got the other [suspension] situation."
Hardin and Buford have missed the past two games for an unspecified violation of team rules. They remain part of a Minneapolis Police Department open investigation, so it's unclear when they could be reinstated.
Penn State ranks 66th in the nation in passing offense (237.3 yards per game) with a first-year starter at quarterback, in sophomore Trace McSorley, and one of the Big Ten's top wide receivers, in Chris Godwin.