TORONTO - Canada's best game at the Pacific Nations Cup rugby tournament ended in a crushing last-second 21-20 loss to Samoa on Wednesday.

After the Samoans scored 13 straight points in the second half to pull ahead 16-13, Canada seemed destined for victory after a slashing Phil Mackenzie run for a try in the 75th minute. James Pritchard's conversion gave Canada a 20-16 advantage with the clock winding down.

Samoa drove down the field and had a lineout five metres out. The danger seemed averted when Canada stole the lineout, only to have the ball pop loose when two Canadians collided. Samoa's Sakaria Taulafo dove on the ball for the try and a 21-20 win.

"A lot of positives but absolutely gutted, to be honest," said Canadian coach Kieran Crowley, whose team deserved better. "The boys, they dug deep. They really put it all in there and then to lose it in the last couple of minutes like that is pretty disappointing from our perspective."

"A lot of emotion in that one," said Canadian captain Tyler Ardron, forced to leave the game in the fourth minute with a knee injury. "I think we played our absolute hearts out. I don't think anyone could have done any better."

Canada, ranked 18th in the world, has now lost all five meetings with No. 9 Samoa.

Winger Alesani Tuilaga, the man-mountain of a Samoan captain, paid tribute to Canada after the match.

"That was a tough game," said the six-foot-two 265-pounder. "We're happy with the result. We know we worked hard for it. Credit to Canada, they gave us a good game, a good run from the beginning until the end. And credit to my boys to keep fighting, believing in ourselves."

Samoa will meet No. 10 Fiji in Monday's final in Burnaby, B.C. Both teams have 2-0-1 records, tying 30-30 when they met last Friday in Sacramento.

Japan (2-1-0) will play Tonga (2-1-0) for third place while Canada (0-3-0) faces the U.S. (1-2-0) for fifth.

One positive for Crowley is that he dug deep into his roster for Wednesday's game, resting many starters in making 12 changes from the team that lost to Tonga. And Canada still nearly got the win.

"We made the changes because we had to find out about a few guys, see if they'd step up," said Crowley. "They're certainly putting the pressure back on us now and they've put the pressure on the guys that didn't play."

Mackenzie, with an assist from teammate Conor Trainor, put Canada ahead after he got to a long cross-field kick from Nathan Hirayama that landed just outside Samoa's 22-metre line and beat a string of defenders to the goalline.

Until then, it had looked like Michael Stanley's long-range kicking would lift Samoa to a comeback win.

The Samoans rallied from 13-3 down at halftime with Stanley tying the game and then moving the Pacific Islanders into the lead with a pair of 45-metre-plus kicks on or near the halfway line.

Canada dominated the early going but blew several chances to increase its first-half lead. Pritchard, Canada's all-time points scorer, also missed two second-half penalty kicks.

The Canadians lost 20-6 to Japan and 28-18 to Tonga earlier in the competition. Samoa beat the U.S. 21-16 and tied Fiji 30-30.

Canada, despite losing Ardron early, came out firing on all cylinders Wednesday and led 13-0 after 13 minutes.

Canada will find out the extent of the injury after a scan Thursday.

"I don't think it's too bad, to be honest. I'm walking around all right," said Ardron. "I'm hoping for the best, hopefully I can play Monday."

He was walking but gingerly and with a giant icebag on his knee.

"It's a concern," said Crowley.

Nick Blevins also scored a try for Canada. Pritchard kicked two penalties and two conversions.

His first penalty, in the third minute lifted his international total to 600 points, the 20th player in world rugby to reach that milestone. Pritchard also took over as captain after Ardron's exit.

Anthony Perenise also scored a try for Samoa. Stanley kicked three penalties and a conversion.

In earlier action at BMO Field on a day of torrid temperatures, Tonga beat the U.S. 33-19 and Fiji, down two men at the end, hung on to defeat Japan 27-22.

The Canada-Samoa game was played to an unwanted soundtrack from the nearby Edgefest 2 concert headlined by Incubus.

Crowley's squad has won two of its last 12 test matches dating back to November 2013. The Canadian men have only beaten No. 21 Namibia and No. 29 Portugal during that stretch.

They lost to No. 9 Samoa (twice), No. 11 Scotland, No. 12 Tonga, No. 13 Japan (twice), No. 14 Georgia, No. 16 U.S., and No. 17 Romania (twice).