As the common wisdom goes, the average length of an NFL career is 3.3 years. Being drafted highly lengthens the average career considerably, but there are still no guarantees for the rookies entering the league this year that they’ll stick around for long.But some rookies have even more to prove than simply why they deserve their roster spot. Here are the five under the most scrutiny.Caleb Williams, QB, Chicago BearsBeing the first overall draft pick promises you nothing but pressure. Will your career path turn out like Peyton Manning’s or JaMarcus Russell’s?Williams may have been one of the highest-graded quarterback prospects in recent history, but now his job is to translate his talent to the big leagues—for a team that chased Justin Fields out of town after 38 starts to make r…