Fighting through a late final round logjam atop the leaderboard, Bill Haas won for the sixth time on the PGA Tour at the site of his first career triumph, squeezing out a one-shot victory at the Humana Challenge.  With the event boasting its strongest field in years, Haas began Sunday’s finale in a four-way tie for the lead with Erik Compton, Michael Putnam and rookie Justin Thomas, then overcame an early 3rd-hole bogey to remain in the hunt throughout the afternoon.  But with none of the overnight leaders going low, the door was left open for men like Charley Hoffman (64), area native Brendan Steele (64), South Korea’s Sung-Joo Park (65), Matt Kuchar (67) and Steve Wheatcroft (67) to all get into the mix.  Indeed, by the time Haas arrived at the par-4 16th, he was in a six-way tie for the lead before holing a clutch 20-foot birdie putt that lifted him one clear.  He then closed with two pars (the second after his drive hung on a bunker lip at the par-5 18th) which, perhaps surprisingly, proved just enough to win by a single shot.............Twenty-six-year-old South African Branden Grace claimed his sixth career European Tour victory and his second of the young 2015 season, winning the Qatar Masters in dashing style in Doha.  Grace began the planned Saturday finale in a four-way tie atop the leaderboard with Scotland’s Marc Warren, Argentina’s Emiliano Grillo and Austria’s Bernd Wiesberger, so a shootout seemed to be in order - and in the end all four men, plus France’s Gregory Bourdy and South Korea’s Byeong-Hun An (both of whom closed with 65) would factor into the mix.  Bogeys at the 2nd and 3rd slowed Wiesberger’s momentum early, and Grillo never really got it into gear, making only two birdies on the day, the first of which came at the 10th hole.  Warren birdied the first two holes but could turn in no better than even par, while Grace birdied the first but only turned in one under, thus allowing Bourdy, An and several others to creep into contention.  But in the end, Grace and Warren both heated up on the final nine to nose ahead of the pack, playing through the 15th hole tied for the lead at 16 under par before Grace unleashed the shot of the tournament, blasting a driver to within five feet of the hole at the 307-yard 16th, setting up a clutch eagle.  Warren would make birdie here, then draw even once more by birdieing the 155-yard 17th, but he was unable to match Grace’s closing birdie at the 589-yard 18th, which allowed the South African to clinch the title.