Diggin has spent his entire career at Franklin's Gardens, coming through the academy ranks to take his place among the elite.
A long-term supporter of the club he plays for, Diggin should have been at Europe's showpiece event when Saints tasted Heineken Cup glory at the beginning of the century. The then 15-year-old schoolboy was all set to head to Twickenham for the clash with Munster before illness struck a cruel blow.
Diggin was hit hard by appendicitis, forcing him to give up his seat and watch from the sofa. Understandably, the teenager wasn't too happy about the way in which fate had conspired against him on the greatest day in Northampton's history.
"I was livid, I had appendicitis the week before," Diggin told the Northampton Chronicle and Echo.
"Dad was taking me and three of my mates, but I had appendicitis and couldn't go.
"One of my friends took my ticket instead and my dad took all my mates for the day. I sat and watched it in my mum and dad's pub. I was absolutely gutted."
That disappointment hit Diggin hard. It should have been a day of massive celebration but instead the England Under 16, 18, 19 and 21 international was unable to enjoy the moment to the full.
Fast forward 11 years, however, and Diggin looks on course for a very different Heineken Cup experience.
The 26-year-old has featured in seven of his side's eight European fixtures so far this term, scoring an impressive six tries having bagged four against Edinburgh in mid January.
Unless illness or injury intervene once more, Diggin should start the May 21 encounter with Leinster at the Millennium Stadium as Northampton look to claim a second Heineken Cup crown.
From schoolboy fan to Heineken Cup hero - it's the stuff dreams are made of. And, at times, dreaming is exactly what it feels like to the 2009 Amlin Challenge Cup winner.
"It's crazy," added Diggin.
"You look back and think 'I used to play rugby with all these guys and they are off doing different jobs now and I am still playing as a professional now'.
"It's weird. You think how many thousands of people in the town aspire to be a professional player and only a couple of people get the opportunity and I'm one of them.
"It's just awesome to be part of this. We have got a great team at the moment and I really, really hope we win something this year."