Paul Casey pulled off a spectacular fightback to reclaim a share of first place in the U.S. Open, as co-leader Rickie Fowler began his second round at Erin Hills.
One off the pace overnight, Casey looked to have dropped out of contention when he followed a birdie at the 11th, his second hole, on Friday by dropping five shots in four holes - a triple-bogey eight at the 14th proving particularly painful.
However, the Englishman rallied brilliantly, birdieing five holes in succession from the 17th to get back to seven under.
Casey duly parred his way home for an eventful 71, finishing his round just before Fowler walked down the first hole seeking to build on his wonderful opening-day 65.
Although winds remained low for a second day in succession, firmer greens and a number of trickier pin positions promised to make low scoring trickier than it had been on Thursday, when a record 44 players broke par.
PGA Tour rookie Xander Schauffele, who matched Casey's first-round 66, made it to seven under on two occasions on Friday, but slipped back into a share of third following a double-bogey at the 13th.
Alongside Schauffele at five under were Brian Harman, Tommy Fleetwood and Brooks Koepka (all afternoon starters like Fowler), Kim Si-woo (70) and amateur Cameron Champ, who was three under for the day through 15 holes.
Bill Haas (68), Harris English (69) and Brendan Steele (69) had moved into the group at four under, where Marc Leishman (72) remained, while Masters champion Sergio Garcia was a shot further back following a 71.
However, both Rory McIlroy and Jason Day were set to miss the cut at five over and 10-over respectively, and Danny Willett withdrew ahead of his second round tee-time, having shot 81 on Thursday.