You can use stats, you just have to explain why they're meaningful. If you can tell me which of these are 1st round picks and which is Lamar without google or looking at my previous post I'll be impressed - stats don't tell a lot of the story for CBs.
59 tackles (36 solo), 1 TFL/Sack, 0 INT, 13 PBU
34 tackles (28 solo), 1 TFL, 3 INT, 9 PBU
40 tackles (30 solo) 4.5 TFL (1 sack), 3 INT, 12 PBU
I said decent, not great. We're obviously going to disagree. But you don't get drafted without being above average at something, and I think he goes a bit before the 5th anyway. Draft stock is not a perfect measure by any means, Stanley Morgan was a very good college receiver and not a great NFL prospect. But being a legitimate draft prospect is at least an indication of physical talent.
I can't prove to you that he's above average, but I have 2 data points that at least lean that way - a second team all conference selection and decent draft stock. You can scoff at the second team all you want, there are 14 teams in the big ten, so say 28 starting corners (although you could factor in nickel corners if you wanted). So according to the coaches he's either 3rd or 4th out of that group, which is one of the better conferences in the country. Believe what you want, but forgive me for not being persuaded by your eye test.