The rain forced the start to be delayed more than an hour Sunday and the hailstorm prompted a delay of over two hours.
A rain delay and bad light forced Mickelson and Casey to return on Monday and the 48-year-old retained his three-shot lead to seal glory at the site of this year's U.S. Open - the only major he is yet to win and has finished as runner-up in six times.
We'll get to some nuggets backing each argument, but let's first hear from the guy whose opinion matters most in all things Mickelson - the ubiquitous lefty himself.
Beginning the day three strokes off the pace, Mickelson matched Casey's birdie at the par-five second and holed a 10-footer at the fourth to cut the lead to two.
What excites him is that he's putting as well as he has at any time in his career and has found an extra "5-6 miles per hour swing speed" he believes that could be the key at the Masters, even if he conceded that winning 50 times on the PGA Tour might prove a challenge. "But I totally get where he's coming from".
Mickelson was bogey-free with six birdies, and he made his big run starting with a 9-iron to a foot behind the cup on the par-4 ninth.
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"Thank you SteelerNation for a big 9 years...time to move on and forward ", Brown said, adding the deuces emoji and #NewDemands . On Tuesday, Brown basically ended his career in the Steel City, and he bid farewell to the organization on Twitter .
Casey was at 15 under, tied with Scott Stallings, who closed with a 66.
"I can see fine", he said to a PGA Tour rules official as they walked up the 16th fairway. Play was suspended on Sunday due to weather and darkness.
"I've written down a goal of winning L.A. and I had an outside chance of winning this one - I had a very good chance of winning this one", Casey said. Casey at least birdied the 18th for a 71 to finish alone in second, the difference of $152,000. He won that summer's British Open at Muirfield and last year's Mexico Championship.
Casey called Mickelson's effort "a phenomenal round of golf" but added: "It's not over yet".
Mickelson claimed his 44th US PGA Tour title and has also won three European Tour titles, the 2004 Grand Slam of Golf and 2004 Skins Game, and a 1993 Challenge Tour event in Paris.
Casey blinked first with a bogey on the 11th hole, and another on the par-3 12th when his tee shot came up short and into the bunker.
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