The pair are among a high-class field of 16 who will contest the two-day knock-out tournament.
Both earned their spot through their fine form in the county’s Order of Merit series, which Calasse won.
He only moved to Norfolk in 2023, joining Sprowston Manor where Diggens was club captain at the time.
Calasse, 43, said: “I was introduced to Karl within the first week and he's basically been my playing partner come practice partner through winter, through summer. He and I have become really good friends.
“We play a lot of golf together. I know his game well, he knows my game well and he's a very good match play player.
“If Karl comes out with the game that I know he can play on a really good day, it will be a close match.
“He's very steady off the tee and his putter is deadly. So if he gets on the green, in regulation, he's going to be a tough opponent.
“It will be friendly, but competitive. We know that there's something on the line. Karl will definitely be playing to win, I'll be playing to win. But we'll both be encouraging each other to play well.”
On paper, Calasse will start favourite for the match-up. The Zimbabwean, who arrived in England just over a decade ago, has had a very good season and earned a Norfolk call-up for the Eastern Counties Foursomes at Seacroft in May.
The plus-2.5 handicap index golfer has also clinched victories at Sprowston Manor and Eaton to help him finish top of the pile in the Order of Merit race.
Calasse said: “I think it's a good achievement for me. Golf has been part of my life, but it's never really been something that I've focused on as hard as I have in the past two years.
“I always knew I had a natural talent of being able to just strike the ball, but being competitive was never part of my golf make-up.
“These past two years have been really competitive golf for me, and it's been an eye-opener, playing with the best players in the county. Playing in the Seacroft competition was a huge eye-opener.
“So, I'm proud with winning the Order of Merit, but I still know there's loads of work to be done.”
Calasse and Diggens will compete among a string of fellow achievers in the end-of-season showdown at Bawburgh where Harry Brister will aim to defend his crown.
County first-teamers, including Ben Rawsthorne, Scott Wright and Sean Rafferty, are in action, as is Norfolk Boys champion Liam Caffyn.
Fellow rising star Jack Johnson will compete in the handicap knockout competition, which runs alongside the scratch championship. Johnson, 15, won the handicap order of merit series – just one of many high points for him in 2026.
Photo (credit Rushmer PR): Warwick Calasse is looking to top off a great season with a strong performance at this weekend’s Norfolk Match Play Championship
Norfolk Match Play Championship
Scratch competition draw
Harry Brister (Bawburgh) v Jacob Jeary (Bawburgh)
Phil Scott (Mundesley) v Jack Bennett (Royal Norwich)
Ben Rawsthorne (Bawburgh) v Charlie Green (Bawburgh)
Karl Diggens (Sprowston Manor) v Warwick Calasse (Sprowston Manor)
Liam Caffyn (Dereham) v Harry Bradfield (Mattishall)
Olaf Gent (Thetford) v Scott Wright (Middleton Hall)
Sean Rafferty (Royal Norwich) v Dan Palmer (Sprowston Manor)
Ryan Clarke (Mundesley) v Alex Day (Bawburgh)
Handicap competition draw
Richard Abbs (Mundesley) v Darren Farman (Great Yarmouth & Caister)
Robert Webb (Bawburgh) v Todd Pitcher (Mattishall)
David Holt (Dunston Hall) v Ian Daywin (Great Yarmouth & Caister)
James Martin (Dunston Hall) v Andy Cranmer (Dunston Hall)
Hugo Fisher-Briggs (Royal Norwich) v William Stursberg (Royal Cromer)
Matthew Bennett (Wensum Valley) v Stuart Goddard (Wensum Valley)
David Fullegar (Sprowston Manor) v Steve Ormston (Dunston Hall)
Paddy Green (Bawburgh) v Jack Johnson (Royal Norwich)