The biggest theme for the Pac-12 in 2014? Passing, passing, passing.

As you surely know if you frequent the Pac-12 blog -- typically considered the University of Oxford of the Internet -- we've been typing pretty regularly about the returning QB talent in the Pac-12. As in 10 returning starters, a group that includes a handful of national awards candidates.

That alone would support the notion of big passing numbers this coming fall. But there's more!

• The Pac-12 is extremely deep at receiver.

• The Pac-12 is questionable at running back.

• The Pac-12 loses many of its top sack leaders from 2013.

• The Pac-12 loses many of its top interception leaders from 2013.

Thus the formula: Experienced QBs plus questionable running games plus questionable pass defenses equals big passing numbers.

Of course, that probably means the teams that can run the ball well and play good defense are going to end up leading the conference.

But here are the supporting facts:

Returning rushing leader from 2013: No. 5 Byron Marshall, Oregon (1,038/86.5 yards per game)

2014 challengers: D.J. Foster, Arizona State; Thomas Tyner, Oregon; Jordan James, UCLA; Javorius Allen, USC.

Breakdown: The Pac-12's top four rushers from 2013 are gone and most conference teams are uncertain that the position. In fact, Foster might be the only certain No. 1 option this coming fall.

Returning passing leader from 2013: Sean Mannion, Oregon State (4,662/358.6 ypg)

2014 challengers: Marcus Mariota, Oregon; Brett Hundley, UCLA; Taylor Kelly, Arizona State; Connor Halliday, Washington State; Jared Goff, California.

Breakdown: With 10 QBs coming back from 2013 -- a number of whom have national pedigrees -- the Pac-12 is as deep at the position as it has been in recent years. And with Arizona and Washington, the two teams with legitimate QB competitions (assuming Utah's Travis Wilson is given the green light by doctors), the supporting casts around the new QB will be strong. As noted: big passing numbers this fall, across the board.

Returning receiving leader from 2013: Dres Anderson, Utah (1,002/87.7 ypg)

2014 challengers: Jaelen Strong, Arizona State; Nelson Agholor, USC; Chris Harper, California; Ty Montgomery, Stanford.

Breakdown: Despite losing the three most productive pass catches from 2013 -- Brandin Cooks, Paul Richardson and Josh Huff, not to mention Marqise Lee -- the conference is overbrimming with receiving talent. Arizona, California, Stanford, UCLA, Washington and Washington State welcome back most of their top guys from 2013, and Arizona State, USC and Utah also are potentially strong at the position.

Returning sacks leader from 2013: Hau'oli Kikaha, Washington (13)

2014 challengers: Tony Washington, Oregon; Kevin Anderson, Stanford; Leonard Williams, USC; Nate Orchard, Utah.

Breakdown: Kikaha and Washington are the only returning guys who ranked among the conference's top-12 in sacks in 2013 (another good sign for conference QBs?). One of the biggest injuries this spring was Utah losing OLB Jacoby Hale.

Returning interceptions leader from 2013: Steven Nelson, Oregon State (6)

Challengers: Marcus Peters, Washington; Greg Henderson, Colorado; Tra'Mayne Bondurant, Arizona; Su'a Cravens, USC; Ishmael Adams, UCLA; Jordan Richards, Stanford; Ifo Ekpre-Olomu, Oregon.

Breakdown: Only two of the top eight interception leaders is back in 2014 (another good sign for QBs?). A few guys to watch out for: Arizona State's Damarious Randall, Stanford's Alex Carter, UCLA's Fabian Moreau and USC's Josh Shaw.