In the end, Phil Mickelson should feel pretty good.

Sure, he failed to close out what would have been his 43rd PGA Tour victory—and his first since winning the 2013 British Open some 938 days ago—with an indifferent chip and a lipped-out five-footer for birdie on the 72nd hole of the AT&T Pebble Beach Pro-Am. The two-stroke lead Mickelson took into Sunday’s play was the 23rd time in his career he had led outright going into a final round. He had converted 18 into victories, but not this one. Then again, he had not led after three rounds since the 2013 U.S. Open at Merion.

Mickelson looked shaken but determined as he walked off the final green, Vaughn Taylor beating him by one stroke. “I played a little bit tighter throughout the round than I wanted to,” he said, pointing out five failed up-and-downs that proved the difference. “It tells me I need a little bit more work. I also know I’m that close. Makes me more determined to get this thing right.”

So here’s the true takeaway: There are strong signs that Lefty, who will be 46 in June, is back to a level of play that makes not just winning but winning majors plausible again. Since switching from Butch Harmon to new instructor Andrew Getson late last year, Mickelson has played well. In his four PGA Tour starts in 2016, he has a T-3, a T-11 and now a second.

Under Getson, Mickelson says he has improved the plane of his swing, which had gotten too flat going back and too vertical coming down, leading to chronic inconsistency. “I was frustrated with the way I’ve been playing,” the five-time major champion said at the CareerBuilder Challenge last month. “I’ve always been very good with irons, very good on par 4s, very good with little touch shots, and all my touch and feel stuff was not being effective because it wasn’t matching up to my swing plane."

Mickelson, however, gave himself an “A” for the way he began playing in the California desert. “I didn’t feel like it’s hard work to hit the ball straight or get it in those fairways,” he said. “And, that allows me to play the way I like to play, which is aggressive.”

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In turn, Pebble Beach was by far his best showing of the year. Mickelson’s opening three rounds of 68, 65, 66 featured his old scoring verve. His swing looked more balanced and powerful, his good drives longer, his iron shots struck sharply and with a penetrating flight. With Mickelson’s spirits higher, his virtuosity with his short game and putting seemed to happen naturally.

Yet, perhaps inevitably with swing changes that haven’t fully hardened, Lefty had lapses. In each of the last two rounds on the Monterey Peninsula, he hit only nine greens, although he saved a 66 on Saturday with only 21 putts and going nine-for-nine in scrambling.

“I got a little bit of work to get my ball-striking back to that level that I need to be for tomorrow’s round,” he said presciently.

On Sunday, Mickelson’s tee-to-green mistakes cost him. Loose bogeys at No. 4, where he fatted a 90-yard wedge, and No. 5, where he pushed an 8-iron, opened the event up to his challengers. A wild drive on the 11th and a poor chip led to a bogey, and on the par-5 14th, he bunkered a misjudged third shot with a wedge that led to a costly bogey.

Working with new instructor Andrew Getson, Mickelson has seen his confidence return as his swing has become more balanced and stronger. (Sean M. Haffey/Getty Images)

Still, Mickelson battled back, making a tough, sliding downhill 10-foot par save on the 16th, and a 15-foot must-have birdie on the 17th to get him within a shot. On the 18th, after two good shots left him only 20 yards from the pin, and with the memory of having chipping in from 33 feet on the same hole a day earlier, Mickelson got under his chip shot. The fluffed flight caused the ball to finish short, and then he missed the birdie on the top side.

The final-round 72 had to hurt, but it’s doubtful Mickelson’s elevated spirit will abate because of a lost opportunity. He was inspired by Pebble Beach, where he had won four times, citing the fact that nearly a century ago, his maternal grandfather, Al Santos, would take a bus from Salinas to caddie at the just-opened Pebble for 25-cent-a-bag loops. “It’s such a spiritual place, if you love golf the way we all do,” he said.

No longer is Mickelson questioning his competitive future, as he admits he did late last year, having finished 61st on the FedEx points list and posting only three top-10s all year.

His focus now, regardless of whether he wins again before April, can legitimately go to the game’s biggest moments. To the Masters, where he has three green jackets, and then to Oakmont, where he will be seeking to complete the career Grand Slam with his first U.S. Open victory (he’s been second a record six times). There is also the Ryder Cup, where Mickelson declined Davis Love III’s offer to be a vice-captain so as not to be distracted from playing his way on the team. He also knows this team will be judged unforgivingly after reforms by his brainchild, the Ryder Cup Task Force.

One way or another, 2016 is going to be a very important year for Phil Mickelson.

Editor's Note: This story first appeared in the Feb. 15 issue of Golf World.