Actually, he probably is quite thankful for Mike Riley.
Jano saw three total carries (all as a freshman) and no touchdowns in three years under Bo. That happened while listed as a running back at the start of his Husker career. Once converted to a fullback for his sophomore and junior seasons, his stats dwindled -- no carries, 1 reception. Only appeared in three total games in 2013 and 2014.
However, his senior year in 2015 coincided with Riley's arrival. That resulted in 42 carries and 3 scores (tack on 58 yards receiving as well).
There's a reasonable chance Janovich would not be playing in the NFL had Riley not given him a chance to show his value to the team. As much as we might not care for Mike Riley, he was an absolute blessing for Andy Janovich.