IRVING — Modern medicine is a marvel, but it’s a masterful putting stroke that cures just about all ills on a golf course.“Fantastic drugs” prescribed by medical professionals liberated Greg Chalmers from a backache, but 22 putts in a round of 5-under 65 on Saturday made the Aussie-turned-Colleyville resident a contender at the HP Byron Nelson Championship.Chalmers, 40, jumped 15 spots to a tie for 10th on golf’s moving day with a 7-under 203 total after 54 holes at the TPC Four Seasons Las Colinas.Saturday also marked a dramatic change in fortunes for Chalmers, who only last month withdrew from the RBC Heritage because of what was diagnosed as an arthritic back. Chalmers missed the cut the past two weeks and was 34th at the Zurich Classic of New Orleans three weeks ago, his best result since finishing 15th at the Waste Management Phoenix Open in February. Entering play at the Nelson, Chalmers had missed the cut in six of his previous 11 starts.Birdies on four of his first six holes set the tone Saturday. He bogeyed seven — statistically, the easiest hole of the tournament — but followed with a fast, downhill 13-foot birdie on eight and drained a 52-footer off the green on No. 9.“You need those kind of things when you’re going to have great days. I got lucky there,” said Chalmers referring to No. 9. “I’ve really rolled the ball beautifully the past two days.”That’s unlike Monday through Wednesday, when the putter “was really ugly,” Chalmers said. He tried six putters in practice, but went back to his “old faithful.”Seeking his first PGA Tour victory, the 15-year veteran hopes consistency appears in his driver, which has suffered. Chalmers hit only five of 14 fairways, but it’s not because of the back.“If it was that bad, I wouldn’t show up,” Chalmers said. “Welcome to golf when you’ve been playing for 20 years. Your back just seems to disagree sometimes.” Left-handers dayChalmers and Mike Weir made sure lefties weren’t the odd men out at the Nelson.Weir, a 44-year-old Canadian and former Masters champion who missed 18 consecutive cuts between 2011-13, was one shot back of leaders Louis Oosthuizen and Brendon Todd.“I’m not paying attention to what anybody else does,” Weir said. “I don’t bomb it like these guys, I can’t cut corners and reach the par-5s like they can … that’s not my game.“You have to keep putting well and have good iron play.”Ace up his sleeveScottie Scheffler became the fourth amateur since 1983 to record a hole-in-one on the PGA Tour.The reigning U.S. Junior Amateur champion from Highland Park aced the 218-yard No. 2 with a 5-iron.“I was in-between a 5 and a 4,” said the 17-year-old, who enters Sunday’s final round tied for 38th at 2 under. “I didn’t want to go short. I hit it pretty solid and it landed up on top, rolled in.”Going lowWunderkind Jordan Spieth maintained a sense of humor despite a somewhat demoralizing 3-over 73 on Saturday that left him out of the running entering the final day.“It’s tough to swallow today’s round,” the 20-year-old said. “We had good conditions and I was confident going in.”The goal today: “59,” Spieth said laughing.Spieth and former Mansfield High School standout Martin Flores, who shot a 1-under 69 on Saturday, will tee off at 8:33 a.m.Briefly• Fort Worth’s J.J. Henry improved his position 20 spots with a 2-under 68 on Saturday. He’s tied for 47th at 1 under.• Tim Herron, who fell off the pace with a 4-over 74, needs to earn $212,444 this week to retain his major medical exemption for the rest of the season. He’ll need to climb 30 spots to eighth.• James Hahn put himself in contention with a second consecutive 65, including five straight birdies on Nos. 12-16. “I feel like I’m rolling the rock pretty good.”• For a third straight day, TPC’s 498-yard, par-4 No. 3 played the most difficult. Over three rounds, the hole has yielded 26 birdies, 223 pars and 144 bogeys or worse. Off the tee, 47 of 394 drives have found the water that guards the right side of the fairway.