NORMAN, OK – SEPTEMBER 11: The Oklahoma Sooner Schooner carries the American flag on the anniversary of September 11 at Gaylord Family Oklahoma Memorial Stadium on September 11, 2010 in Norman, Oklahoma. (Photo by Ronald Martinez/Getty Images)The Oklahoma Sooners are the favorites in the Big 12 once again this season. They’re also expected to compete for the national championship.But that doesn’t mean the Sooners don’t have weaknesses. Every team does, and they aren’t immune.Most would assume Oklahoma’s biggest question mark involves the quarterback position. Baker Mayfield is gone, and it is up to Kyler Murray to replace at least most of his prodigious production.ESPN, however, thinks the Sooners’ most glaring issue is on the other side of the ball.ESPN Big 12 reporter Jake Trotter labeled safety as Oklahoma’s “biggest question mark” in a feature that dropped today.The Sooners should be improved at cornerback, but safety remains a huge concern. Incoming freshman Brendan Radley-Hiles, who starred in the spring, is already assured of manning either nickelback or back safety. But OU will need others to emerge to solidify a secondary that has been unreliable the past two seasons.Oklahoma will face its fair share of prolific passing offenses in the Big 12, so a sturdy pass defense is a must.We’ll see if safety is as big of an issue as Trotter projects it to be.You can read the rest of ESPN’s analysis on the entire preseason Top 25 here.