Hensby and American legend Jay Haas both opened with rounds of four-under 67 on Thursday, 68-year-old Haas bettering his age by one to earn an unlikely share of top spot on the leaderboard.

In a field boasting major champions such Ernie Els, Bernhard Langer, Padraig Harrington, Retief Goosen and Jim Furyk, Hensby might also be considered a shock first-round front-runner yet recent performances suggest a strong showing was in the offing.

Tied for seventh at the PGA TOUR’s Puerto Rico Open in March, Hensby was Australia’s best finisher at the KitchenAid Senior PGA Championship where he was tied for eighth.

Just days out from his 51st birthday, Hensby hit just seven of 14 fairways on Thursday yet was third in the first round for Greens in Regulation, hitting 15 of 18 in regulation at 83.33 per cent.

Six of his 29 putts yielded birdies as he and Haas finished one-stroke clear of Rocco Mediate, Tim Petrovic, Paul Broadhurst and former champion Steve Stricker.

Those who witness Hensby’s rigorous workouts on Facebook know the effort he has put in to be competitive on the seniors circuit and he said it was his recoveries from wide of the fairway that set up such a good score on day one.

“If you don’t drive it in the right areas, then you get it on the wrong side of the greens and it’s very difficult to make a score,” said Hensby.

“Overall the golf course is in great condition, though. If you play well, you can shoot a score.

probably missed my tee shot on

“I tried to hit driver (on 10), and I got a decent sort of a lie (in the right rough). I hit a good shot in there and made birdie.

“That kind of kept the momentum going for sure.”

Hensby’s position at the top of the leaderboard is a far cry from his debut US Senior Open last July.

Battling severe bouts of insomnia, Hensby was forced to withdraw after just 10 holes of the opening round but has returned in a much better state both physically and mentally.

“I had some medical issues last year. I still do have kind of sleep issues, bad insomnia,” revealed Hensby, the 2004 John Deere Classic champion.

“Last year I was up for three or four days before that first round.

“It was unfortunate because I was actually playing pretty well then.

“This year I’ve got it under control somewhat.

“It’s kind of funny how I had to withdraw and now I’m leading. Pretty cool.”

A recent winner on the Legends Tour in Europe, Richard Green made a solid start to be tied for 12th at even par with John Senden and Rod Pampling both in a share of 36th at two-over.

On the PGA TOUR, Cam Davis (65) is tied for eighth three strokes behind Rory McIlroy and JT Poston after the opening round of the Travelers Championship while Kiwi Ryan Fox is tied for fourth at the BMW International Open in Germany.

US Senior Open – Round 1
T1          Mark Hensby     67
T12        Richard Green   71
T36        John Senden      73
T36        Rod Pampling    73
T45        Gavin Coles        74
T64        Robert Allenby  75
T84        Stuart Appleby  76