Paul Casey came home in just 27 shots to move within two shots of the halfway lead at the HP Byron Nelson Championship.
The Englishman’s eight under par back nine led to a 63 and moved Casey into a share of second, two shots behind leader Brendon Todd.
Last week’s Players Championship winner Martin Kaymer and former Masters Tournament winner Mike Weir were also in the group tied for second on six under.
Casey became the eighth player in US PGA Tour history to shoot 27 for nine holes - one off the all-time record of 26 held by Corey Pavin.
"I had no concept of what I was doing," Casey said.
"The seal was broken when I got to 10; it just spiralled from there."
"I like to think I would be pretty good at shooting low rounds of golf through the past, but certainly nothing like that."
Major Champions Padraig Harrington and Louis Oosthuizen were firmly in contention on four under.
