The reigning Horse of the Year had just put away Life At Ten after a mile-long duel for the lead and was bearing down on the finish line.

“I didn’t feel any acceleration and I got worried,’’ Borel said. “She wasn’t really there. I knew if anyone was running behind us, we were in trouble.’’

They sure were. Persistently was kicking into high gear under Alan Garcia, gaining ground with every stride. She took the lead with three jumps to go and won by a length. The stunning finish silenced the crowd 23,347 that turned out to see Rachel Alexandra’s return to the Spa after last year’s electrifying victory in the Woodward Stakes.

The loss was the third in five starts this year for Rachel Alexandra, and leaves racing fans wondering what’s next for the 4-year-old filly who rolled to an 8-0 record last year with victories against the boys in the Preakness, Haskell, and Woodward.

“If she isn’t exactly where she was last year, hopefully she can get back there,’’ Steve Asmussen, Rachel Alexandra’s trainer, said. “I don’t want to give up on getting back to where we were. I don’t.’’

It was Rachel Alexandra’s first race at 1 1/4 miles and her first Grade 1 race of the year. But unlike last year, when her speed seemed to be enough, the same cannot be said for 2010. She now has two wins and three runner-up finishes against less-than-stellar competition.

“We’re just tickled to death to win the race,’’ Persistently trainer Shug McGaughey said. “My hat’s off to Rachel Alexandra. She runs her heart out every time. She made a beautiful presence in the paddock today. We were just lucky enough to pick up the pieces.’’

Life At Ten was third, followed by Miss Singhsix and Classofsixtythree.

Persistently returned $45, $8.10, and $3.60, while Rachel Alexandra returned $2.30 and $2.10 and Life At Ten, the 9-5 second choice, paid $2.10. The winning time was 2 minutes 4.49 seconds.

Persistently, a 4-year-old chestnut filly, has won four of 14 starts and earned $180,000 to boost her earnings to $491,256.

“I thought Rachel might be a little vulnerable going a mile and a quarter, and I knew we’d run a mile and a quarter,’’ McGaughey said.

Asmussen figures the duel up front spelled defeat for Rachel Alexandra.

“I thought Rachel put a very good mare away,’’ Asmussen said, referring to Life At Ten. “It obviously took more out of her on the front end than we would have hoped for. When she moved away from [Life At Ten] that’s what you were hoping to see. Then she got run down.’’