Everything I can find on Lee's broken finger seems to indicate he missed 4 games, then he tried to play through the pain for 1 game, then he sat out the season finale. So I'm not sure how much that explains away the data we do have.
I don't want to make it seem like injuries are the only reason his stats were below average, but I don't think you're giving them fair credit.
In 2015, he played four games, sustained a concussion against Temple, missed the Houston game, broke a throwing hand finger against Navy, missed the following game and then tried to play out the rest of the season. His stats plummeted to a 39.6% completion percentage on 36/91 passing his final three games because of the finger. That particular injury is incredibly difficult to manage as a quarterback. Would a calligrapher be able to maintain their abilities with a broken finger? Unlikely.
Lee very well may be an average quarterback but I don't think his previous stats tell us much at all given his youth, injuries and the competition. They certainly shouldn't be used against him or rendered mostly irrelevant as your tone suggests.