It's not ideal because Barnes is the perfect Nickel. He has great hands and forces a lot of fumbles. You want a playmaker like that as close to the line of scrimmage as possible because that's where most of the action will be and most throws don't go more than 10 yds beyond the line of scrimmage. Unfortunately, I don't think Wes and Conn like their other options at Free Safety. So, because Barnes is the best option there, they have now moved his best playmaker to a spot that's now the furthest away from the ball. That ball that Lewis dropped vs App State would definitely have been a pick 6 if Barnes was in his usual spot.
I'd much prefer Lewis being Terrell and Lukas' backup at CB.