Ohio State's numbers in the category of rushing defense aren't great but those in passing, scoring and total defense are... Alabama's in passing and scoring aren't so good as their rushing and total (defensive numbers posted this season only against FBS teams) but they're still well above average.
Florida State's defensive stats are above average but far from dominant. Oregon has allowed a lot of yards this season...mainly through the air. Their figures against the run are above average with scoring defense their best category of these.
The SOS rankings are as follows: Alabama, Oregon, Florida State, and Ohio State.