Not until you figure in how many top 25 teams the other coaches faced, W-L records of teams faced, and offensive rankings of teams faced. Comparing the last three times Osborne faced Kansas against the last three times Pelini faced Wisconsin isn't exactly a level playing field now, is it?
That being said, Bo's defense couldn't seem to contain a power running game or a roll out quarterback.
Best defensive genius Nebraska has had so far is Mike Riley. His Nebraska teams have never given up a single yard, a single point, or allowed a single pass completion. (See how that works if we don't put things into context?)
Dirk compared Bo to Cosgrove when each played top 25 offenses.
Pelini played 10 top-25 offenses since joining the B1G 2011-14. His defensive averages? 37.3 points, 508.1 yards. FYI - this does NOT include the 2012 Wisconsin Massacre with 70 points and 640 yards allowed. It does include an Aaron Murray-less Georgia in the 2013 Gator Bowl (19 points/416 yards) and a 1st time taking the field Gus Malzahn led Arkansas St (6 points/286 yards).
Cosgrove played 13 top-25 offenses between 2004-07. His defensive averages? 38.7 points, 484 yards.