Popoali'i provided some of the few sparks in a lacklustre Otago effort highlighted by a general lack of basic skills.
He made a couple of sizzling breaks, linked well with midfielder Ben Atiga and tried to create something out of nothing when his side struggled to breach the halfway line.
Unfortunately for Popoali'i, the lasting memory of his performance will be an extraordinary - and excruciating - attempt at a cross kick inside his own 22m in the final minute. The kick went backwards and its target, loose forward Paul Grant, was whistled for a knock-on.
It was the sort of afternoon for Otago where not much went terribly wrong, but little went particularly right, either.
There were worrying signs of the general malaise that seemed to infect the side last year, particularly noticeable when Otago was trying to create attacking moves.
An early injury to captain Eben Joubert did not help, though replacement TJ Ioane - in his unique, scattergun style - made ground with the ball, Kees Meeuws provided some grunt and young No 8 Gareth Evans tried hard.
Tony Brown and rookie second five-eighth Jayden Spence had their moments but too often lacked support.
Otago scored the first try, through Ioane, after an Atiga break, but Northland led 13-10 at the break following a controversial Joel McKenty try, when the television match official ruled he had got the ball down after it had been scooped back by an Otago player.
Popoali'i created Otago's second try with a well-timed dash, leaving Meeuws to burrow over from close range.
But Northland completed the scoring when All Black discard Rene Ranger made a scorching break, and the ball was spread to Lachie Munro.
Otago had late chances but could not quite capitalise on them, leaving it to contemplate a second loss after the highs of the wins over North Harbour and Auckland.
"We just weren't quite as accurate in all facets of the game as we were previously," Otago co-coach Phil Mooney said.
"I wouldn't say we lost because of defence or attack or whatever. Just across the board, we weren't as accurate as we needed to be."
Otago had an appeal to the TMO turned down, when replacement prop James McGougan was ruled to have been pushed into touch in goal.
Northland, though, got a break with the unusual McKenty try, when there appeared doubt over whether he should have been allowed to play the ball on the ground.
"I didn't think so and I questioned the ref after the game," Mooney said.
"The TMO said the guy was lying in goal, so there's no offside line. I think one of our guys still had his hand on the ball. But I guess it's academic now."
THE SCORES:
• Northland 20
Joel McKenty, Lachie Munro tries; Munro 2 con, 2 pen
• Otago 17
TJ Ioane, Kees Meeuws tries; Tony Brown 2 con, pen
• Halftime: Northland 13-10.
