Whatever becomes of Boise State’s final season in the Mountain West — a brief tenure that may, unbelievably, end without an outright conference title — the short stint in the league has robbed the Broncos of one thing that may never come back: their home invincibility.

The signature blue turf at Bronco Stadium was the ultimate security blanket. A most unwelcome mat for foes, who left bruised, battered and mostly blown out.

The stadium isn’t a college football cathedral and, yes, it lacks for tradition and seats and amenities. But it was a place no opponents wanted to set foot in — at least not if they wanted a victory.

In 10 seasons in the Western Athletic Conference, the Broncos never lost a league home game (40-0). Between 1999 and 2010, the Broncos lost just twice on their slice of blue heaven — both to BCS-conference teams (Washington State in 2001 and Boston College in the then-MPC Computers Bowl in 2005).

But that sheer dominance went away when the Broncos switched leagues. The new foes in the Mountain West weren’t awed by Bronco Stadium — or the team inside it. They weren’t scared by the blue turf. And just in case anyone thought there was some magic in the Broncos’ all-blue attire, the league banned that.

In its first visit to the blue, TCU ended the 35-game home winning streak last year. Some Boise first-graders had never been alive for a Boise State home loss.

But at least the Horned Frogs were headed to a BCS league and had a championship pedigree. A loss to them was heart-breaking, but understandable. It came down to a missed field goal, after all.

Saturday night, however, San Diego State — carrying with it no championship pedigree and a lackluster football history — walked into Bronco Stadium and showed just how awed it was by the place by returning the opening kickoff 100 yards.

So much for intimidation. So much for a fired-up crowd. So much for Boise State’s ranking, its conference title hopes and BCS dreams.

San Diego State wasn’t going away. Not on this night. Not in this place. The Aztecs, winners of four straight, just kept coming and coming. They didn’t let the Broncos develop any sort of offensive rhythm. They made the big plays on special teams.

Whatever BCS ambitions the BSU faithful entered Bronco Stadium with were quickly replaced with a sense of concern, of worry, of dread. The same feeling that no doubt existed in the hearts of fans in Reno in 2010 and against TCU in 2011.

Boise State’s 78-3 record at home since 2000 — the best in the nation — didn’t mean much. Didn’t mean anything, really. Not with the run game floundering in the second half. Not with San Diego State picking up key first downs in the final quarter.

And then, suddenly, it was over. There would be no last hurrah, no missed field goal at the end. There will be no BCS — and maybe not even a conference title.

There was just a stadium emptying out. Quietly.

“We just didn’t play well enough. Bottom line,’’ coach Chris Petersen said.

Beaten. Simply beaten. No kicker to blame. No individual to pin it on.

Just the home team beaten in a place where the Broncos never used to lose.

© 2012 Idaho Statesman Brian Murphy: 377-6444