The OL is a major issue. Brown has been rather open about the fact that the staff feels that now only 6 guys are fully ready to play. And the lack of depth is not about injuries. 1 RS Frosh who was expected to be 2nd team C is hobbled - that's the only OL injury.
Making it worse, Billy Ross is not playing this fall, and will graduate and play elsewhere in 2021. Ross as RS Frosh in 2018 started 11 games. He was no Frosh All-American, but for a Frosh he was sound and showed glimpses of better things. Mack's OL coach Stacy Searels immediately demoted Ross in Spring 2019, even though the OL in 2019 would be young and inexperienced. Ross barely played the first half of the season.
Before UNC, Searles was OL coach at Miami for 3 seasons. Before that he was OL coach at VT for 2 seasons. Fans at both places were unimpressed with Searles, complaining about his failure to develop talent, his failure to develop OL depth, and his choices for both starters and players off the bench, as well as his recruiting, the recruits he was focused on and those he was willing to pass on.