Ian Book was good in 2018, too, and it’s sometimes expected that players are better in their first season as a starter than their second. Book’s passing yards and touchdowns were well up in 2019 from 2018. Book’s interceptions were down. He also ran much better in his second season. This is probably because he threw 85 more times in 2019 than 2018, because it wasn’t his completion percentage. That dropped from 68.2 to 60.2 percent.
Struggling to complete passes is where Book regressed. Had he maintained his completion percentage, then he would have taken the leap that everyone had hoped he would.