Leeden (54), the owner-manager of Home Plus in Dunedin, won the inaugural Shanghai event last year when he beat New Zealand squad members Andrew Kelly (Canterbury) and Mark Watt (North East Valley) in the final at the Dunedin Bowls Stadium.
The three original finalists are back and will be the favourites in the 48-strong field.
Leeden is an experienced bowler and is one of the few New Zealand bowlers to have reached the second round of the PBA world championships at Potters Leisure Resort in England.
Other noted bowlers in the field include Alvin Gardiner and New Zealand representative Shayne Sincock, from Christchurch, Ross Stewart (Riverton), former South Otago bowler Roger Barron (Leith), Doug Thomas (North East Valley), former New Zealand junior pole vault champion Simon Nyhof (Hawea) and senior champion Robbie Gibson (Taieri).
There is a sprinkling of women bowlers in the field, the most notable being Trish Marr (St Clair), Pam Walker (Taieri), Tracy Penty (Logan Park Business Women), Rachel McDowall (Andersons Bay) and Sue Smeaton (Taieri).
The Shanghai bowls tournament is a quick-fire, shorter version of the game and was invented by former international Ken Walker, who hopes it will become the bowls equivalent of twenty/20 cricket.
Three players are on the mat together in a singles match and six points are available on each end.
The closest bowl gets three points, the second bowl two and the third closest bowl one point.
The first player to 31 points wins the game.
It is a time-limit game that lasts just 1hr 15min.
A Shanghai is when a player scores the maximum of six points on a single end.
A feature of the game is the joker that can be used once in a game by each player.
It must be called before the end starts and it doubles the points scored on an end by that player.
"It is a novel, exciting and quick game," Walker said.
"There is a place for it in bowls."
Because of the success last year in Dunedin, Walker has turned it into a national event, and full fields will contest tournaments in Pukekohe, Frankton and Hastings on Saturday.
The winners of the Pukekohe and Frankton events and the first two place-getters at Hastings and Dunedin will contest the national final at Dunedin, from September 3 to 5.
"We have opened the tournament up to non-PBA members," Walker said.
"It will give them a taste of playing bowls indoors during the winter months."
The New Zealand PBA season will start on Sunday and Monday at the four venues.
It is a qualifying tournament for the Scottish International open singles.
The finals weekend at Dunedin in September will decide New Zealand entrants to several events on the World Bowls Tour in the United Kingdom.
The winners will compete at the Scottish and Welsh International open singles, and two players will join the richest carnival in bowls at the Potter's Leisure Resort in England, for the world indoor singles and pairs.
Depending on sponsorship availability in the United Kingdom, there may yet be another trip on offer if the international open singles is reinstated to the World Bowls Tour calendar.
Another highlight this year may be an Australia versus New Zealand PBA challenge at the Tweed Heads club, on the Gold Coast, from July 19-21.
