With soft fractions giving the front-running Ziyarid things his own way, the Grade I $400,000 Secretariat Stakes was his to win on Saturday afternoon.
But Treasure Beach proved why he was the 3-2 favorite in the 1¼-miles turf test for 3-year-olds.
The European English-bred ship-in, trained by world-renowned Aidan O'Brien, caught Ziyarid at the wire for a neck victory before 31,069 fans at Arlington Park.
"Of course, we were 100 percent concerned (chasing Ziyarid's slow fractions)," said Charlie O'Connor, the director of sales for Ashford Stud who represented trainer Aidan O'Brien and owners Derrick Smith, Mrs. John Magnier and Michael Tabor.
"We needed a good strong gallop on the lead and didn't get it. But he still won."
And won with a time of 2:03.91, bettering Cape Blanco's clocking of 2:05.39 in the Arlington Million.
"Colin O'Donoghue gave him a great ride," O'Connor said after Treasure Beach's first race in the United States. "He gave him a great ride and thank God that he did.
"Our goal is to stand him here in America so this is very exciting to win a Grade I stakes here."
Trainer Alain de Royer Dupre was delighted by Ziyarid's American debut at odds of 8-1.
"He was beaten by a true Group I horse," said de Royer-Dupre of Treasure Beach, who won the Irish Derby. "I think our horse proved himself."
Trainer Tom Proctor's Banned finished third, 1¾ lengths ahead of fourth-place finisher Willcox Inn, who was trying for a sweep of the Mid-America Triple Crown after wins in the Arlington Classic and American Derby.
Part owners of Willcox Inn are St. Viator High School graduates Marty Nixon, Ron Lepinski and Al Lepinski.
The local star was rated well by jockey Robby Albarado and made a move toward the front on the final turn but was unable to sustain it in the stretch drive.
"I thought I got him in a pretty good spot," Albarado said. "But then at the last part of the race he wasn't making up any ground.
"But then again, those were some pretty good horses that finished in front of me. I can't make any excuses. I thought he was getting over the ground OK."