Smith ultimately fell frustratingly short in his quest for victory in Pennsylvania, but will leave Aronimink Golf Club with renewed belief after producing his first top-10 showing at a major since the 2024 Masters.
After threatening to nab the lead all day, a final-round two-under-par 68 left Australia's one-time world No.2 five shots shy of fast-finishing English winner Aaron Rai.
At four under, he tied for seventh with superstars Rory McIlroy and Xander Schauffle after making the gut-wrenching call to part ways with his lifelong coach Grant Field after missing a sixth straight majors cut at last month's Masters.
Despite missing out on the winner's spoils, Smith's new partnership with Claude Harmon III, the son of Tiger Woods' former swing guru Butch Harmon, paid immediate dividends this week.
"We've just managed to clean up a few things that were perhaps a little bit off, and I feel like I've got a lot more confidence in my swing," Smith said after recording the 10th major top-10 result of his career.
"Even out there today, under the pressure, I felt like I was able to trust it already. So lots of positive signs.
"I feel like I've thrived in major championships my whole career. I've been able to play my best golf in major championships, and that kind of fell off.
"I don't think it was from a lack of hard work. You just lose a little bit of confidence in your swing and maybe in your brain, and it can all happen so quickly.
"That's why I needed a fresh voice in the head and almost a restart."
Alas, bidding to become the first Australian to add the Wanamaker Trophy to the Claret Jug, the 2022 British Open champion couldn't buy a putt a on the back nine on Sunday.
Smith shaved the hole on four occasions and his failed 18-foot attempt to match Justin Thomas's clubhouse lead epitomised the 32-year-old's disappointment.
In the end, Rai stormed past Thomas anyway.
Smith was nevertheless heartened to have collected three front-nine birdies to pull within one stroke of the lead and feel the tension and excitement of being in contention on the back nine on Sunday.
"It was good. I love that stuff. That's why we compete," he said.
"We compete to win, and it was nice to get the heart rate up and feel your hands and your legs get a little bit jelly. It was cool.
"And I'm happy with how I played with all that going on as well. So lots of positive stuff."
Fellow Australian Min Woo Lee never contended after starting the final round alongside Smith at two under and in a tie for 11th.
Lee closed with a one-over 71 to settle for his equal best finish at a PGA Championship, in a share of 18th with triple major winner Jordan Spieth and two-time champion Padraig Harrington.
Jason Day closed with a 72 to finish tied for 65th at six over, while Elvis Smylie (71) was equal 75th at eight over. Â
13°C