There had been much discussion between both Mickelson and Casey as to whether play should be completed in regulation time on Sunday but despite the logistical issues involved in carrying the final two holes over to Monday, common sense prevailed.
Car headlights may well have been needed to complete the event on Sunday and even then that might not have been enough.
Mickelson, Casey and their amateur partners were the only players on the course when play was eventually called on Sunday, an earlier delay for hail preventing them from finishing in time.
Mickelson had been keen to finish but Casey felt he needed to give himself the best chance to catch the American and also protect the lead he and his partner had in the pro-am contest.
On their return, Casey finished off his 16th hole by holing a 3-footer for par before both produced stunning tee shots at the par-three 17th although each would miss their very makeable birdie chances.
With his three-shot lead still intact, Mickelson understandably played the 18th conservatively by laying up, before a brilliant third shot from 140 yards left him only 6 feet from the hole, which he then proceeded to hole.
Casey had found the edge of the green with his 2nd at the last and also made birdie but the gap was too great.
It's Mickelson's 44th PGA Tour title overall and has sparked hope of a career grand slam for the 48-year-old when the US Open returns to Pebble Beach in June.
The American first won at Pebble Beach in 1998, completed his 4th title in 2012 and has also been runner-up on one other occasion. He joins Mark O’Meara with the leading number of wins at the Pebble Beach Pro-Am.
Pebble Beach is a place of spiritual meaning for Mickelson with family ties going back to 1919 which he explained afterwards in an interview with Peter Kostis from CBS.
Scott Stallings had finished the previous evening as had the rest of the field and his 3rd place was confirmed once Mickelson and Casey finished on Monday.
Jason Day and Korea’s Si Woo Kim tied for 4th, Day recording his fifth top-six finish in the event in his last seven appearances.
Day’s last round of 68 promised a little more than it delivered but it was yet another fine week for Day at what must be one of his favourite venues.
“It was nice to be able to finish it off with a birdie," said Day when finishing off on Sunday evening and still unaware of the final result.
“I just made a couple of errors on the front side. But to be honest, I thought if I could get in with a 68 or 67 today that might do it, but unfortunately, the guys in front are playing some pretty good golf here, especially Phil.
Curtis Luck finished 28th, Matt Jones 53rd and Cameron Davis 59th while John Senden and Adam Scott also made the cut but missed out on playing on Sunday after the field was reduced due to field size.
For Luck, it was his best finish in eight starts as a PGA Tour cardholder.
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