Coach Cory Brown said he was encouraged by the performance of his side in the pre season match and thought Otago probably deserved to win.
The visiting team was in front until Trent Renata, who played for Otago last year, scored a try. He nailed the conversion to confirm the win for Tasman.
It was a good first up effort from Otago against a team that had a fair sprinkling of Super rugby players.
Otago scored some nice tries and matched the intensity of the Tasman side, a team that made it all the way through to the premiership final last year.
Brown said the team went up a level, which was needed against a side like Tasman.
''It was a good performance right across the park. We did some stuff which was really encouraging,'' he said.
''We took a good step up from last week and the physicality from the guys was really good. We got caught out of alignment a couple of times on defence but our front on tackling was really good.''
Brown said he was happy with the set piece, and Otago scored a couple of nice tries off lineouts and scrums.
''It was encouraging, as it is always tough to come up here. We travelled on the day and it is always a long way to get up there.
''Then we lost Jackson Hemopo quite early on and that put a bit of pressure on our locks and loose forwards, as we only took 22 up.''
Hemopo suffered a cut to his face when he caught a boot from behind attempting a tackle. He ended up getting stitches in his eyelid but it should not affect his prospects of getting straight back on the park.
Otago stood strong for most of the game on defence and then showed some nice touches on attack.
Brown said No8 Mika Mafi had a powerful game in his first appearance at this level. He made some strong carries and got to the advantage line.
Matt Faddes had a strong all round game at centre for Otago, while fullback Tony Ensor scored a nice try in the first half and was tidy throughout.
Ensor has had a frustrating past couple of seasons with injury and will be looking to get a clear run in the No15 jersey for Otago this year.
Winger Gavin Stark came off after his hamstring tightened during the game but it was only precautionary.
There were no other injury concerns, although the side had a delayed return yesterday with fog descending on Nelson Airport.
Brown was hoping for a quick recovery, as the team takes on Southland in its final warm up match at Riverton on Wednesday.
Otago's first game of the ITM Cup is against heavyweight Canterbury on August 15 at Forsyth Barr Stadium.
Otago v Tasman
The scores
Tasman 31
Shane Christie 2, Trent Renata, Mitchell Scott, Pete Samu tries; Renata 3 con
Otago 25
Tony Ensor, Matt Faddes, Mifa Maki tries; Peter Breen 2 pen, con; Fletcher Smith con
Halftime: Otago 13-7.
