They were very big moments. Watling went on to scored 37 from 30 and combined in a 57-run partnership with Daryl Mitchell to put Northern on course for victory.
Styris only scored 11 but he helped the team knock off some of the 51 runs it needed to win from the last five overs.
But it was Mitchell who carried Northern to victory with an unbeaten innings of 46. Scott Kuggeleijn smashed 22 from seven balls in an important cameo. He also hit the winning runs, lofting Holder down the ground for six.
Earlier, the Volts made sedate start but had at least preserved wickets until Hamish Rutherford (16) was caught ball watching in the sixth over and could not make his ground when Neil Broom called him through for a quick single.
Aaron Redmond sliced his first scoring shot. Who could blame him. Legspinner Ish Sodhi was getting plenty of turn and it was not long before he got his man.
Redmond shimmied up the wicket and sliced another shot but this time found Jono Boult at a fly slip position. Good bowling, great plan and even better execution.
At the halfway stage the Volts were 59 for two and in desperate need of a spark.
Enter Ryan ten Doeschate. There really is a picket fence at Seddon Park and ten Doeschate cleared it twice early in his innings.
But just when it appeared Otago was building some momentum, Broom holed out at long on for 44 from 38.
Otago coach Vaughn Johnson sent Holder out next on a bit of a hunch and with a free license to lash out. He was bowled defending and looked more suited to No 11 than No 5.
Any hope of a decent score died when ten Doeschate (36 from 24) miscued a drive off the bowling of wily veteran Styris. The 38-year-old was miserly yet again, taking one for 16 from his four over stint.