Cabrera, whose closing birdie knocked 19 players, including four-time runner-up Phil Mickelson, out of the final two days, held the lead over Watson, who shot a 71. Cabrera was 2 strokes up on Australia's Aaron Baddeley, England's Justin Rose, Canada's Stephen Ames, and Sweden's Niclas Fasth.
Casey, whose 66 was the lowest score of the week, stood alone at 143, followed by a five-player group at 144 headed by David Toms, who finished poorly for the second consecutive round and came in with another 72.
The players expected to contend at the start of the week had their share of problems but were still in it. Tiger Woods posted six bogeys in a round of 74 that left him at 145, while Jim Furyk was keenly disappointed after a 75 put him at 146.
Defending champion Geoff Ogilvy was at 146, Vijay Singh at 148, and 1994 Oakmont Open champion Ernie Els at 149. All have work to do today and tomorrow.
Cabrera, 8 for 8 in made cuts at the Open, stuck a sand wedge from 135 yards out to two feet on No. 9, his final hole of the day, and made the putt for his third birdie. His other birdies came on long putts - 24 feet at No. 13 and 35 feet at No. 16, both par 3s.
"I've had two very good rounds," Cabrera said through an interpreter. "At the beginning, I didn't think I was going to be here [in the lead] at this moment. But at this point, I'm going to try to make the most of it."
Watson, who leads the PGA Tour in driving distance but is looking for his first victory, did his best to stay patient and keep his driver in the bag on Oakmont's tight fairways. He hit 5-irons and 6-irons off the tee and carded four birdies and five bogeys.
"You could say [my length] is helping me a little bit," said Watson, who is from Bagdad, Fla., near Pensacola. "I can just hit shorter clubs into some of these holes and maybe hit it a little bit higher to stop it. But I'm just happy to hit them straight right now."
However, the round that had everyone talking belonged to Casey, who went from a tie for 104th place after the first day to sole possession of seventh. He started his day making a 45-foot birdie snake at the impossible 10th hole and following with four birdies and a bogey.
"Right now, because it's fresh in the memory, without a doubt it's the best round of golf I've ever played," said Casey, who attended Arizona State and has a home in Scottsdale. "I've shot lower numbers. I've holed out shots. But there is no rest out there. So I'm ecstatic with that."
The British delegation is making an impact. Nick Dougherty held the first-round lead with a 68, although he slipped to 77 yesterday, but Casey and Rose, who shot his second straight 71, are in prime position for the weekend.
No one from the United Kingdom has won a U.S. Open since Tony Jacklin in 1970.
"I think the odds are beginning to stack up, not in our favor, but there are more guys who can now do it each week or each major that comes around," Rose said. "I don't think it's necessarily on our minds, but every time all of us arrive here, we would love to be the first to go ahead and do it for sure."
Contact staff writer Joe Juliano at 215-854-4494 or email@example.com.