Casey carded a superb final round of 66 at Harding Park and it took an inspired display from Collin Morikawa to deny him a first major title, the 23-year-old chipping in for a birdie on the 14th and making a spectacular eagle two holes later in a closing 64.
A tie for second place with 54-hole leader Dustin Johnson is Casey’s best result in a major on his 64th attempt and bodes well for his chances in this season’s two remaining majors at Winged Foot and Augusta National.
The 43-year-old finished 15th when Winged Foot previously staged the US Open in 2006 and has recorded five top-10 finishes in the Masters, including three in a row from 2015-17.
Asked why he looked so comfortable in posting four sub-70 scores at Harding Park, Casey said: “Probably because I’ve spent three months where I didn’t touch a golf club, hanging out with my kids, my family at home.
“Then I started practising, but even those four-plus months I spent at home, I’m thinking a lot you know, figuring out what’s important to me.
“When I’m out here, I think those of you who come out and talk to me a lot, you know this isn’t the most important thing in my life. Today (Sunday) was just sort of cruise around the golf course and have a great time.
“I’ve not played great golf so far this season, so anything was going to be a bonus on where I was a week ago or two weeks ago. So I was just out there kind of having a good time.
“But I do think I’m in a sweet spot. It’s taken me 43 years to get there, but yeah, pretty chilled out, know what I’m capable of and enjoying my golf.”