IRVING, Texas (AP) -- Louis Oosthuizen is still looking for a remedy for his recurring back issues.
A victory at the Byron Nelson Championship would sure make him feel much better.
"The last year and a half was really frustrating," he said.
Oosthuizen birdied four of the last five holes for a 6-under 64 on Saturday and a share of the third-round lead with Brendon Todd. The 2010 British Open champion had the low round of the day after recovering from bogeys on two of the first four holes.
"I made a nice birdie on 5, and just really made some good putts," Oosthuizen said. "Every opportunity I had for birdie I actually made. My eye was good today, and I hit a lot of them really close."
Todd who made 12 consecutive pars before holing a 4-foot birdie at No. 18 for a 68 to match Oosthuizen at 10-under 200.
On the morning of the Nelson's final round last year, Oosthuizen withdrew because of a neck issue. He missed extended time last season, and is still bothered by the back even though he won at home in South Africa in January.
Mike Weir, James Hahn and Gary Woodland were a stroke back.
"That's what I've been working toward the last few years, to get myself back here in this position, and looking forward to the challenge," said Weir, the 44-year-old left-hander.
Weir, the 2003 Masters champion who hasn't a top-25 finish since 2010 when the Canadian had an elbow injury, shot 67 while missing 4-foot putts on Nos. 15 and 16. Hahn's 65 included five birdies in a row on the back nine, and Woodland shot 66 with a double bogey at No. 7.
Morgan Hoffmann twice fell out of the lead after hitting drives left into the water and making double bogey, at Nos. 11 and 18. He finished with a 68 and was tied for sixth at 8 under with three-time major champion Padraig Harrington, Marc Leishman and Graham DeLaet.
Todd's only bogey was at the 420-yard fourth hole, when his approach went over the green and he two-putted from 8
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