(Updates at end of round)
May 16 (Reuters) - Paul Casey came within one stroke of the PGA Tour scoring record for nine holes when he stormed home in 27 shots in the second round at the HP Byron Nelson Championship in Irving, Texas on Friday.
Casey was in danger of missing the cut after a mediocre start but turned on the afterburners to end the day only two strokes behind American leader Brendon Todd at the TPC Four Seasons Resort.
"I found it difficult (early but) I broke the seal, made an eagle on (hole) number seven and then the hole started to get bigger and bigger," the Englishman told reporters after picking up an eagle and six birdies on the inward nine for a seven-under-par 63 in ideal morning conditions.
"I hit some wonderful shots on the back nine (although) I got some lucky breaks here and there."
Only American Corey Pavin, who shot an eight-under 26 on the front nine at Brown Deer Park during the 2006 U.S. Bank Championship in Milwaukee, has posted a lower nine-hole score on the PGA Tour.
Casey's 27 matches the tour record for a back nine, emulating Nick Watney (2011 AT&T National), Brandt Snedeker (2007 Buick Invitational), Billy Mayfair (2001 Buick Open), Andy North (1975 B.C. Open) and Mike Souchak (1955 Texas Open).
Casey sank a couple of long putts, including a 30-footer for eagle at the par-five 16th, but most of his birdies came from precise approach shots.
He ended the day in an eight-way tie for second along with German Martin Kaymer (67).
Todd, who has never finished better than sixth on tour, birdied the final two holes after superb approach shots to shoot 64 and set the halfway pace on eight-under 132.
Casey was ranked as high as third in the world in 2009 before injuries and the turmoil of a divorce sent him plummeting out of the top 150.
But the 36-year-old from Cheltenham has worked his way back towards the top echelon in the past year and on Friday it all came together.
"I've had comments the last couple of weeks (from) guys saying you're hitting it a long way," he said.
"I'm kind of smiling to myself because I used to hit it a long way and it's been a couple of years since I've done that. I've really struggled (but) I'm loving my golf right now."
Former world number one Kaymer showed no signs of a victory hangover following his Players Championship win on Sunday as he drained four birdies and one bogey in his 67.
(Reporting by Andrew Both in Cary, North Carolina; Editing by Mark Lamport-Stokes / Ian Ransom)