Leading 27-5 with 20 minutes to go, the home side could say it had put in a praiseworthy effort but it slipped in the last quarter, dropping off tackles and letting Tasman back into the game.
That fact was not lost on Otago coach Phil Mooney after the game.
"I was disappointed in the last 20 minutes where we seemed to go to sleep. Tasman seemed to dominate the physical contest then and we weren't there," Mooney said.
Otago dominated the territory and possession in the first half and led 17-5 at the break.
But silly errors, the scourge of the past few seasons, came back to plague the side as the game wore on. Eight changes by Otago at halftime did not help.
Mooney felt Tasman had shaded his side in the battle for possession at the breakdown, and said his players were not accurate, both in approaching the ruck and delivering the ball.
But it was still a win, and there was plenty to like in this performance.
The scrum was rock solid all afternoon and gave Tasman plenty of headaches.
Prop Kees Meeuws threw his frame around, and was strong in the scrum as Tasman struggled to get any quality ball from its feed.
The support play was also good, with some clever passing and getting over the advantage line the key to a good try to fullback Chris Small in the second half.
The defence was mainly effective, and Otago did a nice job of recycling the ball when needed.
Winger Ryan Shortland, one of the few to play the 80 minutes, ran hard, and set up the first try to livewire flanker Eben Joubert.
Shortland broke the Tasman defence at halfway then passed to halfback Sean Romans, who set Joubert up for a dive under the posts.
After 25 minutes, Otago had its second try as the ball popped out from a ruck and No 8 Paul Grant ran 30m down the sideline to score. Glenn Dickson knocked over the tricky conversion.
Former Southland prop Fai Mika scored Tasman's try in the dying moments of the first half, thanks to a break by winger Kade Poki.
After Small's effort, replacement back Josh Tatupu went over for the final Otago try midway through the second half after he showed the defence a clean pair of heels following a nice pass from Dickson.
Tasman scored tries through back Jack Umaga, who was shifted on to the right wing, before stand-out openside flanker Jonathan Poff found some space down the blindside with two minutes left.
Poff was the best for the visiting side, while Poki looked dangerous every time he got the ball.
Mooney will name his 28-strong squad for the ITM Cup today.
OTAGO v TASMAN
- The scores
• Otago 27 - Eben Joubert, Paul Grant, Chris Small, Josh Tatupu tries; Glenn Dickson 2 con, pen.
• Tasman 15 - Fai Mika, Jack Umaga, Jonathan Poff tries.
• Halftime: 17-5.
• Crowd: 350.
