19.Oct.2014 Mike Riley is 13-41 vs Top 25 teams
Here is the link.
They list his record as 13-39, but that was before the USC and Utah games. 13-41 comes to a winning percentage of 24.
To be fair, there are some good coaches on that list with losing records. Bob Stoops stands out to me as having the most success versus good opponents. His record is impressive.