America’s fastest horse this season, as judged by many speed-figure enthusiasts, is on display today at Churchill Downs. And it’s not reigning Horse of the Year Curlin, who will be paraded during Saturday’s closing card before heading to a stud career.

Rather it’s Commentator, the even-money favorite for today’s $400,000, Grade II Clark Handicap.

The 7-year-old gelding won Saratoga’s Grade I Whitney Handicap this summer, earning a Beyer speed figure of 120. That came three years after he captured the Whitney for the first time with a 123 “fig.”

By way of comparison, Curlin ran a career-best 119 in last year’s Breeders’ Cup Classic. Big Brown‘s best was a 109 in the Kentucky Derby.

“When you see a horse with Beyer figures of 120 or more — and he has three in his career — that’s superstar status,” said journalist Dick Jerardi, part of the team that computes Beyers, which assign a number to assess how fast a horse runs a race, taking into account track condition. “I can count on 10 fingers the number of times probably in the last decade that we’ve put a number of 120 or more out there.”

” … For Commentator to do that as a 7-year-old, I’m sure that’s unprecedented. To do it in ’05 and come back in ’08, that’s kind of astonishing.”

Commentator is enjoying his best stretch in a 20-race career that includes 13 wins (only one by less than 4 3/4 lengths), $1,841,936 in earnings and a lot of starts and stops, most due to a shin that twice has required surgery.

The gelding was born the same year as 2004 Derby and Preakness winner Smarty Jones, but that champion already was retired when Commentator debuted as a 3-year-old at Saratoga.

“If he stays around next year, he could be the George Foreman of racing and get his due,” said trainer Nick Zito, whose 2009 goal is a third Whitney, which would match Commentator with Kelso as the oldest horses to win the stakes.

“Longevity will put him in perspective. We’re not going to be Kelso or Forego, but if you’re mentioned in that breath, that box, if you get in that circle, you’ve got to feel good.”

Commentator, owned by Kentuckian Tracy Farmer, won his first five starts by a combined 45 lengths, including by nine in a Churchill allowance. After his first defeat, the gelding was sidelined six months, returning to win the 2005 Whitney by a neck over Horse of the Year Saint Liam.

Commentator ran once more and was off 10 months, then ran twice and was off nine more months.

His only defeat in five 2008 starts was his second place in the Met Mile after setting a blistering pace. Commentator captured his second Whitney by 4 3/4 lengths over Pimlico Special winner Student Council, then romped in the Massachusetts Handicap by 14.

“He had the fracture, so many other things, but he got through them,” Zito said. ” … He’s an incredible machine.”

Commentator faces seven in the 1 1/8-mile Clark, including turf standout Einstein and $2.5 million-earner Magna Graduate. Zito also is running Pennsylvania Derby winner Anak Nakal.

“Commentator doesn’t even have to be loose on the lead; if they don’t do too much too early, he’s hard to run down,” said Scott Blasi, chief assistant to Magna Graduate trainer Steve Asmussen. “He’s obviously had a lot of problems through his career, (but) 7 years old and running at this level, that says a lot. They don’t come around like him very often.”

Zito’s aversion to California’s synthetic surfaces is no secret, but he said he was truly conflicted whether to run Commentator in the Breeders’ Cup Classic at Santa Anita last month. Ultimately, he didn’t want to run the gelding back in five weeks.

“After the race, we certainly knew we made the right choice,” Zito said, referring to the European grass horses Raven’s Pass and Henrythenavigator blasting to 1-2 Classic finishes with their explosive late kicks.

“However, I had been torn. I thought, ‘He’s like the second-best horse in America, with Big Brown out of it.’ … You say, ‘Wow, this is a tough thing to give up.’… But it didn’t matter anyway. He needed the time.”

Though Farmer is a Breeders’ Cup board member, he said it made no sense to overrule his trainer and run at Santa Anita.

“And who knows?” Farmer said. “Commentator may be trying for the Breeders’ Cup in 2010 at Churchill.”