His maiden first-class five-wicket bag was the catalyst for Otago's unlikely four-wicket win against Auckland at the University Oval yesterday.
Test opener Hamish Rutherford also played a key role in the victory with a hard-hit 74 from 45 deliveries. Michael Bracewell backed up from a first innings hundred with 45 from 48, and Ryan Duffy completed a strong match with a second half-century.
But it was Jacb Duffy, younger brother of Ryan, who turned the course of the game. The right-arm seamer picked up three quick wickets following the lunch interval to break the stalemate.
The visitors appeared to be grinding their way towards safety before Jacob (five for 57) blasted out Brad Cachopa, Tarun Nethula and Dean Bartlett, to complete his five-wicket haul.
All three were cracking deliveries. He got the ball to reverse and hit the stumps. Cachopa got an inside edge and played on. The other two were just beaten.
It was a great feeling for the 20-year-old.
''I'd been thinking about it a lot. I've played 18 games now and it had been weighing on my mind that I hadn't taken a big bag,'' he said.
''To get a five-for today felt bloody good and in a game where it actually helped the team win.
''It was a deck which did nothing the whole game. We just had to keep chipping away. I thought that was probably my last spell, if we didn't take a wicket then.''
There was even talk of bringing the tea break forward 30 minutes, so the game could be called off early. But Jacob struck and the match took on a different complexion.
When Michael Bates edged to gully, Auckland had slumped from 254 for four at lunch to 280 for nine all out.
Auckland captain Rob Nicol was not fit to bat. He was struck by a Neil Wagner bouncer on Wednesday and retired hurt.
The visitors achieved a lead of 255 with a minimum 50 overs to bowl, setting up an exciting finish.
Otago openers Aaron Redmond and Rutherford launched an all-out assault, adding 50 runs from 31 balls.
Redmond smacked a towering straight six which clattered into the sightscreen. But it was Rutherford who was really causing alarm.
The odd early streaky shot aside, he punched the ball crisply down the ground or through point for a series of boundaries, racing to 50 off 29 balls.
He did not ease off when Redmond holed out for 26, either. The team 100 came up off 72 balls, as Rutherford kept the pressure on.
But his innings ended in disappointing fashion when he swatted a full toss from Nethula straight to Robbie O'Donnell at midwicket.
Bracewell skied a sweep shot to gift Nethula a third wicket, and when Jesse Ryder dragged a delivery on to his stumps, Auckland would have sensed an opportunity.
But former skipper Derek de Boorder (36 not out), who had a tremendous game with the gloves, was a reassuring influence, while rookie Ryan Duffy (57) continues to develop nicely.
The win means Otago (71 points) has leapt up the competition ladder into second place, with three rounds remaining.
• Canterbury has gone to the top of the Plunket Shield table following a comprehensive 301-run win against Northern Districts in Christchurch yesterday.
Northern resumed at 48 for five, chasing an unlikely 486 runs for victory.
Leg spinner Todd Astle picked up three wickets to wrap up the innings after Matt Henry had earlier taken four for 29.
