In Brussels on Friday, 25-year-old Walsh will line up against the top eight throwers from the Diamond League standings, with US$50,000 ($69,400) at stake for the winner.
Crouser heads the Diamond League standings on 31 points, with Walsh second on 22.
Walsh has sharpened up for the northern season finale with a 21.50m win at the World Challenge meet in Croatia on Tuesday (NZT), 15cm better than runner-up Damien Birkinhead of Australia.
The Zagreb meeting, while missing Crouser, included Kovacs (20.85m) and Zunic (20.66m), who finished fifth and sixth respectively.
Walsh's victory backed up his win a week earlier at the Diamond League meet in Birmingham, where his winning 21.83m topped second-placed Crouser's 21.55m.
The Timaru builder will be defending his Diamond League title, which he took last year under the now-defunct points system.
He'll also be keen to shake off the groin strain which has plagued him since just before the world championships, and better his all-time best of 22.21m set almost exactly a year ago in Zagreb.
- NZN