If Thomas becomes rattled and makes critical mistakes, unranked Tennessee can upset the seventh-ranked visitors.
Now for the other side of the coin:
Thomas has some elusiveness, and Vol fans are acutely aware of the agony mobile quarterbacks have caused the Big Orange in recent years - no matter who the defensive coordinator happened to be.
Florida's Tim Tebow burned John Chavis' defense for 61 rushing yards in 2007 and UAB's Joe Webb for 78 yards in 2008. Tebow skewered Monte Kiffin's defense for 105 pre-sack yards in 2009. And UT fans surely haven't forgotten how Ole Miss' Dexter McCluster (282 net yards) and Kentucky's Randall Cobb (101) torched Kiffin's crew in wildcat-type packages last November.
Oregon's Thomas probably isn't as gifted a runner as any of the guys mentioned above but he still poses a serious threat because of his speed.
"The quarterback's extremely fast," Vol linebacker Austin Johnson said. "He's not afraid to tuck it and run. We definitely have to be looking for that."
Facing an attack that piled up 720 yards and 72 points last weekend is cause for concern. Facing two Oregon running backs with 4.4 speed is cause for concern. Facing an offense that spreads the defense all over the field is cause for concern. Facing a team with all of the above AND a mobile quarterback ... well, that's cause for alarm.
"It adds a lot (of pressure)," Johnson said, "because you can't be thinking the running back has the ball all the time. The quarterback can keep it and break one on you at any time. If we have that down and know who our responsibility is, we should be able to stop it."
You notice he said "should be."