Materiality trots around the track during a workout at Belmont Park, where on Saturday the colt will try to prevent American Pharoah from sweeping the Triple Crown races. (Julie Jacobson/Associated Press)

Racing fans have many reasons to admire American Pharoah. The colt possesses high speed, which he displayed in the Preakness. He is a battler, as he proved in the Kentucky Derby. He always puts forth a top effort; he has scored six straight victories by a combined 30 lengths.

As he bids to win the Belmont Stakes, American Pharoah possesses not only superior credentials but also a potentially significant tactical advantage. Against a field with a shortage of early speed, the favorite has the potential to take the lead and control the race from start to finish.

Yet despite all American Pharoah’s obvious strengths, I would counsel casual fans and serious players not to bet him — except possibly for a $2 souvenir ticket on what might be history’s 12th sweep of the Triple Crown. I will play the Belmont by taking a stand against the favorite; he won’t be on any of my exacta or trifecta tickets.

The factors that have foiled more than a dozen Triple Crown bids since 1978 apply as forcefully to American Pharoah as to the horses who failed before him. Moreover, there are elements of his own racing record that suggest he is not as invincible as he may look on paper.

Modern-day thoroughbreds are different from the racehorses of the 1970s, when Secretariat, Seattle Slew and Affirmed swept the Triple Crown. They are less robust, and they need more time to recuperate between races. Trainers recognize this fact and manage their horses accordingly. In the Breeders’ Cup Classic last fall, every one of the entrants came into the race with a minimum of five weeks’ rest since his last start.

Yet the 3-year-olds in the Triple Crown series must adhere to a schedule that is rooted in tradition and is out of place in contemporary racing: two weeks between the Kentucky Derby and Preakness, then another three weeks to the Belmont. Horses used to handle this schedule routinely. Now the regimen is formidably difficult. Since 2006, a total of 14 horses have contested all three legs of the Triple Crown. All of them — including six favorites — lost the Belmont.

The difficulty of winning three stakes in five weeks is heightened by the fact that the final leg of the series is 11/2 miles. I wrote in a column earlier this week that no U.S. horses are bred to run this demanding distance on the dirt, thus producing many unforeseeable results. (The average price on the Belmont winners since 2000 has been 17 to 1.) American Pharoah’s pedigree suggests he may be even less suited to 11/2 miles than some of his competitors. The female side of his family tree is dominated by sprinters with minimal stamina.

American Pharoah cannot necessarily overcome these challenges because he possesses dominating talent. He has never been forced to overcome adversity; in his six-race winning streak, he has never had a straw in his path. He got a perfect trip in the 18-horse Kentucky Derby field. He won the Preakness over a muddy track that four of his seven rivals, including his two main challengers, couldn’t handle. It may have appeared that he was finishing strongly in these two victories, but he wasn’t. He ran the final quarter mile of the Derby in a slow 26.57 seconds and the final fraction of the muddy Preakness in the equivalent of 27.62 seconds for a quarter mile — hardly an indication that he wants to go a longer distance.

If American Pharoah is indeed vulnerable, this could be another Belmont that produces a crazy long-shot winner. But three of the favorite’s challengers have credible handicapping merits.

●Materiality won the Florida Derby in March with a Beyer Speed Figure of 110, the best by any 3-year-old this year. He broke poorly in the Kentucky Derby, got caught in traffic and was unable to employ his speed, then rallied belatedly to finish sixth, running the final quarter mile in 25.48 seconds. Trainer Todd Pletcher has given him five weeks to prepare for the Belmont, just as he did with another lightly raced 3-year-old, the filly Rags to Riches, before she scored an upset in 2007. Materiality will probably have the tough job of putting pressure on American Pharoah in the early stages of Saturday’s race, but he is quick and talented enough to do so. (If he applies so much pressure that the two colts get involved in a hard duel, such a scenario could lead to an upset by a stretch-runner.)

●Frosted captured the Wood Memorial Stakes with a solid late run, but the Kentucky Derby didn’t develop favorably for him. Three good speed horses separated themselves from the field, set a moderate pace and finished 1-2-3, with American Pharoah winning. Frosted was the best of the stretch-runners, rallying to finish fourth.

●Keen Ice is a plodder who has never won anything except a maiden race, but he rates a long-shot chance. In the Derby, as he was trying to launch a rally, he was caught in traffic, and when he finally found running room, he accelerated sharply to finish seventh. His Eclipse Award-winning trainer, Dale Romans, excels with long-distance runners and has scored some of his major victories at 11/2 miles (on grass).

None of these three challengers can provide the outcome to the Belmont that most racing fans want to see. But in the event that American Pharoah fails in his quest for the Triple Crown, those fans might want to play an exacta box of Materiality, Keen Ice and Frosted to cushion their disappointment.

For more by Andrew Beyer, visit washingtonpost.com/beyer.