Reason No. 8,683,951 why a horse has been unable to sweep the Triple Crown in 37 years was offered Saturday in West Virginia, of all places.

The Charles Town Classic was supposed to be little more than a $1.5 million workout for Shared Belief, the practically perfect 4-year-old gelding who came into the race as the frontrunner in the race for 2015 Horse of the Year honors.

Then the unthinkable happened. After an unusually sluggish start that had Shared Belief lingering at the back of the field on the backstretch, he was out of view of those watching the track's video feed when announcer Jeff Cernik said the words that generated severe shock waves across the racing industry: "Pulling up, out of contention, is Shared Belief."

Sent off as an odds-on, 3-10 favorite, Shared Belief was pulled up by jockey Mike Smith, who sensed something was wrong after the Santa Anita Handicap winner stumbled a bit coming out of the gate and wisely opted to play it safe with such a beloved champion. "He just seemed to slip in behind and wasn't comfortable," said Smith, whose prudent and caring actions may have saved the horse from further injury. "The safe thing to do at that point was to get back in one piece."

A track veterinarian said the gelding had some swelling in the right stifle, and his owner, sports talk radio/TV host Jim Rome, later announced on Twitter some news that soothed the frayed nerves of an entire industry: "Shared Belief is up and walking around in the barn. He is off in his behind. Vets have been w/ him. Does not appear to be life threatening."

The early prognosis was highly welcomed, yet the CT Classic and a Kentucky Derby development earlier in the day illustrate why so little can be taken for granted in horse racing.

With the Run for the Roses two weeks away, trainer Bob Baffert lost a Derby starter, though, thankfully for the sanity of the sport's most fervent supporters, it was not either of the race's two favorites in the Hall of Fame's stable. One Lucky Dane -- not American Pharoah or Dortmund -- suffered a condylar fracture that will prevent the Santa Anita Derby runner-up from running on May 2 at Churchill Downs in the world famous opening leg of the Triple Crown.

And so, in a span of about 12 hours, we were reminded of how fragile a Thoroughbred can be and how they can sometimes make the Bulls' Derrick Rose look like an iron man ala Cal Ripken Jr. or Lou Gehrig.

That's just one of the many reasons why no one has been able to pull off a sweep of the Kentucky Derby, Preakness or Belmont Stakes since Affirmed notched his hat trick in 1978. Just get getting to one of those of races is a challenge -- much less winning all three of them -- and Shared Belief, who did not run in any of last year's Triple Crown races, is a poster boy for that. It's a dynamic that explains why anyone with a Derby contender will be holding their breath until their horse walks onto the track at Churchill Downs and the band starts playing "My Old Kentucky Home."

Lest anyone forgets, a week before American Pharoah was supposed to breeze to an easy victory in last year's Breeders' Cup Juvenile, an injury knocked him out of the race.

That surely paints a gloomy picture about the prospects of anyone ending an insufferable 37-year Triple Crown, but racing always seems to find a way to generate optimism.

As good as last year's crop of 3-year-olds turned out to be -- with Shared Belief, California Chrome and Bayern leading the way -- this year's class seems even more advanced and talented.

No less of an expert than Steve Cauthen, who rode Affirmed to Triple Crown glory in 1978, sees great potential in this year's group and wonders if it's finally time for a long-awaited sweep to happen.

"You know it's a really good year. I think a horse will win the Triple Crown [again] and this could be the year," Cauthen said earlier this week during a teleconference on behalf of Derby Experiences and the Permanently Disabled Jockeys Fund. "American Pharaoh or Dortmund may turn out to be the horse that can do what we have been waiting for all these years. Looking at American Pharaoh he looks like he could be a freak; the way he won the Arkansas Derby was very impressive. At the same time, Dortmund is a really solid horse. I was impressed with the Santa Anita Derby victory. He actually looks like a horse that can continue to improve. It will be interesting. As a whole this is probably one of the best bunches for a long time."

Perhaps from all that talent and potential someone might emerge who can overcome the odds and make three trips to the winner's circle in five weeks. It won't be easy -- Saturday reminded us of that. Yet it has happened before and it will happen again. When is the operative word, especially with those 8,683,951 question marks attached to the end of it.