The day was going swimmingly for Otago, which recorded two wins in the morning to claim third seeding - thus avoiding powerhouse Canterbury - for the semifinals.
But a rare hitless effort against Marlborough led to a 3-0 loss and an early trip home.
The semifinal was a battle of attrition and locked at 0-0 after five innings when Marlborough pounced, scoring all three of its runs in the bottom of the sixth.
Otago will look back with some frustration on a game in which its errors (four) far exceeded its hits (zero). The lack of offence let down pitcher Ben Watts, who had coughed up just five hits through seven innings.
''We just couldn't really get in the game,'' Otago coach Aran Bailey said.
''It was a real tussle for a while. But Marlborough created a couple of opportunities and we struggled to get anything off their pitching.''
Apart from the unfortunate finish, it was a reasonable tournament for Otago, which rebounded from two losses on the opening day with back-to-back wins, over Marlborough (4-1) and Nelson (4-3), in the round robin.
The star of the Marlborough win was Ryan Williams, who blasted a solo homer in the second inning and a triple in the sixth. Mitchell Finnie added an RBI single.
The Nelson game had a great finish, with two of the Watts brothers featuring prominently.
Otago took a 2-0 lead when Mark Edmunds hit a two-RBI single, but Nelson scored runs in the second, fourth and sixth innings.
Gary Pointon had an RBI double for Otago to make it 3-3, before the Watts boys staged a grandstand finish in the seventh. Ben Watts singled, then stole second base and scored the game-winning run on a Cam Watts hit.
On Saturday, Otago had opened with two losses, one frustrating (5-2 to Southland) and one clearcut (10-0 to Canterbury).
Otago out-hit Southland nine to four, with Williams and Doug Hill each grabbing two hits, and Cam Watts whacking a two-RBI double. But Southland made its blows count.
Hopes of another win over Canterbury to match last year's massive upset were soon shelved, as the Red Sox scored four runs in the first inning, one in the second, two in the fourth and three in the fifth.
Otago's sole hit was a double to Gary Pointon, as the home pitching of Aiden Cocker and Regan Manley proved too good.
Bailey was reasonably happy with his side's performance at the tournament. Saturday had been a mix of rustiness and frustration, but the two wins yesterday boosted morale.
''Today was all about defence and scoring a couple of good runs when we had to get them.''
Ben Watts pitched the bulk of four games for Otago and performed well. There was also a big opportunity for Jacob Wedlock, who pitched the must-win game against Nelson and gave up just five hits in seven innings.
Canterbury beat Marlborough 3-0 in the final.
