Six notable second-round stats from Golf World contributing writer Brett Avery, who compiles the Rank and File statistical sections for the magazine's major championship coverage. For more numbers throughout each round, follow him on Twitter (@BWAvery):
--Rory McIlroy was 37 months old when Gil Morgan became the first player to reach double-digits under par in a U.S. Open (he did that in 1992 at Pebble Beach). Morgan was 45 when he birdied the third hole in the third round to make 10-under, added two more birdies to reach 12-under to lead by seven, then collapsed with a closing 81 to finish in a tie for 13th.
--More McIlroy: If you're searching for a weakness through two rounds (other than his double-bogey on the par-4 18th hole on Friday), consider his play at par-3 holes. While he was three under at par 5s and eight under at par 4s, he lacks a birdie at a par 3 (although he hasn't bogeyed any, either). Going into the week, McIlroy ranked 61st on the PGA Tour this season in par-3 performance (3.15, 11-over cumulatively), but 183rd in birdies or better at par 3s (8.33 percent).
--Six back at the midpoint, Y.E. Yang's 68-69 included four bogeys: two at the 11th, one each at the 13th and 18th. This is the first time he has made the cut in an Open in three tries, and the first time he has shot consecutive rounds in the 60s in a major.
--Looking forward to their third-round pairing, Yang has played the first through fifth holes a cumulative one under par (birdie at the second Thursday, nine pars). By comparison, McIlroy has played the same stretch three under (birdied the first Thursday, the fourth both days). McIlroy also birdied the sixth hole in both rounds.
--Patrick Cantlay and Richard Henley shared low amateur honors at even-par 142 thanks to rounds of 67 and 69, respectively. Cantlay, who just completed his freshman season at UCLA, shot 30 on the back nine in the second round of his Open debut. Henley could become the first to win the low-amateur medal in back-to-back Opens since Phil Mickelson (1990-91) after a tie for 16th last year at Pebble Beach.
--When play was called at 8:04 p.m. (Eastern), the second-round scoring average was 73.110. Surprisingly, there were more eagles recorded in the incomplete round than triple bogeys or worse (6-4). The second-round average was, almost to the thousandth of a stroke, nearly a shot better than Thursday's field performance (74.109).