Beginning a year in which he intends to be the rare American to play full-time on both the PGA and European Tours, Brooks Koepka broke through for his second major victory in less than three months by taking the Waste Management Phoenix Open by one shot, in Scottsdale.  Already a winner of the E Tour’s strong-field Turkish Airlines Open in November, Koepka was little noticed over the first two days here, posting rounds of 71-68 to trail halfway leader Martin Laird by seven.  His fortunes seemed little different when he turned in one-under-par 34 on Saturday before he kicked things into gear, reeling of six birdies at holes 10-17 en route to a 64 which, by day’s end, stood him only three behind Laird and firmly embedded within a crowded group of pursuers.  Laird would stumble late on Sunday and end up carding a 72 to tie for fifth, but by this time the leaderboard was crowded enough that five players held at least a share of the lead over the final hour of play.  Initially it was Bubba Watson and Hideki Matsuyama who looked like winners, but after playing his first 13 holes in six under par, Watson came up a stroke shy after driving the 322-yard 17th but three-putting for par.  Matsuyama, meanwhile, holed a 129-yard approach shot to eagle the 1st hole, but he too would finish one behind, doomed by a three-putt bogey at the par-4 14th.  Koepka, meanwhile, stood one off of the eventual winning number before holing a 50-foot eagle putt at the 553-yard 15th, the stroke that would prove the margin of victory.  Notably, Arizona State junior Jon Rahm closed with rounds of 66-68 to finish in a tie for 5th………………In an event that might well have been an epic shootout had he instead been home in Northern Ireland watching on TV, world number one Rory Mcilroy dominated a strong field to record an impressive first win of 2015 at the Dubai Desert Classic.  Despite the fact that he trailed first-round leader Bernd Wiesberger by two after opening with a 66, there were few moments during the week when McIlroy didn’t seem in command, particularly after he carded a bogey-free 64 on Friday to nose into a one-shot 36-hole lead.  If there was ever a fleeting moment, it came during Saturday’s back nine, when McIlroy drove the ball somewhat wildly but scrambled effectively, eventually scratching his way home in 66 to build a four-shot 54-hole lead.  Thus Sunday proved something of an anti-climax, as McIlroy played steady, aggressive-but-safe golf, aiming to exploit the par 5s (he birdied three of them) while otherwise taking few chances, with the result being that he was never seriously challenged.  Sweden’s Alex Noren, who missed nearly all of 2014 with wrist surgery, mounted Sunday’s best charge, birdieing three of the last four holes to shoot 65 and climb to second, three in arrears.  Two-time defending champion Stephen Gallacher closed with 69 to take solo third, while a quintet headed by Wiesberger and U.S. Open champion Martin Kaymer shared fourth.  But the futility of their collective efforts were best stated by runner-up Noren, who said simply: “"I never even thought of winning, Rory's playing so good”.  And so he was.