The door has been thrown open. Cal Poly can either get in line to step through or watch it close.

Spurned by Wednesday’s hasty departures of Fresno State and Nevada, as well as Boise State’s decision to leave for the Mountain West Conference in June, Western Athletic Conference commissioner Karl Benson said the WAC has started an immediate search for replacements.

Cal Poly was one of the schools Benson mentioned in an 80-minute marathon teleconference with reporters Thursday, opening an avenue to the WAC that was seemingly shut down a month and a half ago.

Lumping the Mustangs, Sacramento State and UC Davis in one sentence, Benson said he’s had conversations with the Football Championship Subdivision trio in the past about making the jump to the Football Bowl Subdivision.

“They’ve indicated an interest and desire at some point in time to make the move,” Benson said. “Whether this is the time, those are institutional decisions that have to be made on those three campuses.

“But if they expressed an interest in making the move, I think the WAC would certainly entertain and look at them as bona fide potential candidates.”

Other FCS schools discussed in the teleconference were Montana, Texas State and the University of Texas at San Antonio, a first-year FCS independent coached by Larry Coker that is expected to make the jump to the FBS in the next four years.

Benson did say the conference might first look to current FBS schools — perhaps even give preference to those in the vicinity of isolated WAC member Louisiana Tech — to avoid dealing with the transitional rules facing FCS programs, but the conference has a history of grooming FCS teams.

After gaining national exposure and winning two BCS bowl games, Boise State is the poster model. Nevada is another of the WAC’s FCS success stories.

“There are FCS schools in the WAC footprint that very well could be the next Boise State,” Benson said.

The question, as Benson said, is whether they are ready.

It seemed like a blessing in disguise to Cal Poly when Benson put WAC expansion on hold after learning Boise State would be the lone defection in the wake of a failed Pac-10-Big 12 coup in late June.

The WAC could certainly function with Fresno State, Nevada and remaining members Hawaii, Louisiana Tech, San Jose State, Idaho, Utah State and New Mexico State.

And the Mustangs, still needing to fund raise for increased scholarships and an NCAA-mandated stadium expansion, would have more time to gain momentum before committing one way or the other.

But when the news broke Tuesday of BYU leaning toward leaving the Mountain West to become a football independent, the conference responded by adding Fresno State and Nevada a day later, and the situation has accelerated.

Now down to six teams, the WAC is two short of remaining a viable FBS conference beyond 2011, and Benson said he was already receiving calls from interested schools Thursday morning.

Cal Poly athletic director Alison Cone said Cal Poly was not one of them.

“There’s no direction yet determined, but we are aware of options,” Cone said. “We’re involved in various discussions that could lead to opportunities to stabilize the program, which would be a great thing to all of Cal Poly athletics.”

UC Davis athletic director Greg Warzecka took a similar stance.

“All of us, every week we get caught by surprise by how quickly things change,” Warzecka said. “Our position here is just to continue to watch the changing circumstances, learn more about what’s going on and any opportunities that are going to present themselves.”

Currently in the five-team Great West Football Conference, which does not receive an automatic bid to the FCS playoffs because of its history of revolving membership, Cone has been on the lookout for better footing for her program for a while.

The Great West guarantees only four conference games, and the chance to ease the difficulty of scheduling seven nonconference contests on a yearly basis could be enough to entice Cal Poly to leave the Big West, where all but four of its other 19 sports happily compete.

UC Davis is also a Big West member playing football in the Great West, and the Aggies and Mustangs share similar economic roadblocks to leaving the FCS behind.

The maximum number of football scholarships allowed in the FCS is 63. FBS schools are allowed up to 22 more. The athletic department from each school would have to independently raise enough money to pay the extra tuition.

That’s not including any scholarship adjustments a school may have to make to remain compliant with Title IX.

After completing a multi-million-dollar renovation four years ago, Cal Poly’s Alex G. Spanos Stadium currently seats 11,075. NCAA rules require FBS teams to maintain a rolling two-year average per-game attendance of 15,000.

Just to add the seats necessary to comply, Cone said recent estimates have ranged from $9 million to $30 million — and well above depending on amenities.

“I think we have some people who would be very interested in the project if we decided to go that route,” Cone said. “It’s an appealing project for the community, alumni, for lots of people.”

UC Davis’ Aggie Stadium, which seats roughly 12,000, has the acreage to add more than 20,000 additional fixed seats, but the expansion would be costly for a department that cut four sports because of budget concerns in April.

University presidents ultimately make the decisions, and Cal Poly is in a transitional period of leadership.

Former president Warren Baker stepped down this summer after 30 years at Cal Poly, and after one aborted hiring search, the university appointed retired Ohio administrator Robert Glidden as the interim president.

New to California, Glidden has held positions in Ohio, Florida and Indiana.

Cone said any recommendation to Glidden would depend on the exact circumstances, which remain unsettled.

“My recommendation would be to find the best situation for our football program and our entire athletic department,” Cone said. “Until we know what options are out there, I’m not too sure what it looks like yet.”