The Englishman was making his fifth start in as many weeks and his debut appearance north of the border, where he closed with an 8-under 64. At 20 under, Poulter finished alone in third place and one shot out of the playoff where Jhonattan Vegas beat Charley Hoffman.
Poulter started the day five shots off the lead, but vaulted into contention and at one point set the clubhouse mark after rolling in a number of birdie putts without dropping a shot.
"The best thing I did today was start holing a few putts," Poulter told reporters. "I played good golf today. I gave myself a lot of chances. I'm going to rue a couple of chances out there on the golf course, 13, 16, where I felt I had opportunities to add to my under par tally today."
The result is just the latest in a string of high finishes for Poulter, who seemingly was without a PGA Tour card after the Valero Texas Open. But a points recalculation gave him a start at The Players Championship, where he finished second, and he hasn't finished worse than T-45 in eight starts since, including a T-14 at The Open.
While the third-place showing won't be enough to lift Poulter into the top 50 in the world rankings to earn him a spot at next week's WGC-Bridgestone Invitational, the glass is certainly half-full for the former Ryder Cup star.
"I'm trending in the right direction," Poulter said. "I'm gaining a bit more confidence with each week I play right now, I'm playing a lot freer than I did three months ago. When you don't know if you're going to be playing the following week, or what tour you're going to be playing on, it's not easy to play golf. I've certainly eased off the pressure."