Allrounder Mitchell Santner gets the plaudits for his first ODI wicket at Edgbaston, from Kane Williamson, left, and Brendon McCullum.

Kane Williamson has hit the top of the charts and will next month take over from Ross Taylor as New Zealand Cricket's highest-ranked player and potential $350,000 man.

Williamson is understood to be No 1 on the top-20 contract list to be released on Wednesday, ensuring an annual retainer of $200,259 starting on August 1, a week before his 25th birthday. Young allrounder Mitchell Santner is the other big winner after an impressive England debut and will earn his first NZC contract, with Grant Elliott and Doug Bracewell expected to return to the top-20 and Ish Sodhi, Colin Munro and the retired Kyle Mills the likely three to drop off.

Taylor was last season's top-ranked player, sources confirmed, but will drop to No 4 or No 5 on the latest rankings compiled under a set formula by coach and chief selector Mike Hesson. Players are ranked on recent performance, and on their likely contribution in the next 12 months, with tests receiving a 50 per cent higher weighting than one-day or T20 internationals. Those ranked 18-20 each get retainers of $81,461.

It wasn't a huge surprise that Williamson emerged on top, with Trent Boult and captain Brendon McCullum understood to round out the top-three, followed by Taylor and Tim Southee.

Match payments increase to $8287 per test, $3592 per ODI and $2348 per T20 international. Assuming he appears in every Black Caps match in the next 12 months, which is tentatively seven tests, 17 ODIs and 13 T20 internationals (not including World T20 semifinals or final), Williamson could earn $149,597 which would take his total from NZC to a tick under $350,000, before prizemoney and IPL and English county contracts.

Williamson was at the peak of his powers in England, scoring a test century at Lord's then 396 runs at 79 in the five ODIs, the most by any New Zealander in a one-day series, as he boosted his world ranking to six in ODIs (career average 47.4) and seven in tests (career average 45.7).

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Boult will have pushed him close after being the equal-highest World Cup wicket-taker with Australian Mitchell Starc. He climbed to third on both the test and ODI bowling rankings before suffering a stress related injury to his back which will rule him out of the August tour of South Africa.

The likely three changes are the fewest in recent memory, reflecting stable selections and a hugely successful 2014-15 highlighted by the Black Caps' run to the World Cup final.

Left-armer Santner, 23, was picked for the England tour for experience but ended as their first choice spinner in the wake of Daniel Vettori's retirement. The Hamilton Boys' High School product, also studying mechanical engineering at Waikato University, looked a composed, accurate limited overs bowler with subtle variations and should feature prominently, with his power hitting an added string to his bow.

His inclusion will likely be at the expense of his Northern Districts team-mate Sodhi who was clearly headed by Mark Craig as the No 1 test spinner.

Elliott's World Cup form demanded inclusion, while the jury remains out on Munro as an international batsman. Bracewell, who was impressive on test return against Sri Lanka in January, deserved a recall while Neil Wagner may have clung on to his contract despite slipping down the test pecking order.

Fellow left-armer Ben Wheeler could be the unlucky one after an impressive start in England, with Wagner's reliability and durability in his favour. Nathan McCullum and Mitchell McClenaghan will remain on the payroll but slide down the order after disappointing tours of England.

The contract list will worryingly contain several players sidelined by injury: Boult, Corey Anderson, Jimmy Neesham (all back) and Adam Milne (heel), while a sore Southee could also miss the African tour to get his body right.

Likely NZC contract list (in ranking order): Kane Williamson, Trent Boult, Brendon McCullum, Ross Taylor, Tim Southee, Martin Guptill, Corey Anderson, BJ Watling, Tom Latham, Adam Milne, Matt Henry, Luke Ronchi, Grant Elliott, Mark Craig, Jimmy Neesham, Mitchell Santner, Nathan McCullum, Mitchell McClenaghan, Doug Bracewell, Neil Wagner.

Money tree: The top-ranked player receives an annual retainer of $200,259, dropping in increments to $81,461 for numbers 18-20. Match payments are $8287 per test, $3592 per ODI and $2348 per T20I.