INTERNATIONAL Bowl hero, Winning Partners, faces a crunch test at Sha Tin this afternoon if he is going to take up an historic invitation to represent the territory in Japan next month. The Neville Begg-trained gelding faces a star-studded line-up in the feature Sassoon Challenge Cup. And Begg said last night: ''He'd have to run prominently to justify taking him to Japan.'' Begg went on to explain: ''We were delighted to accept the invitation to run in Japan but we said at the time it was with the proviso that we were happy with him. ''The test of that comes tomorrow for two reasons. For one thing it would not be sensible to take a horse overseas to compete that wasn't at his best form at home. ''Secondly, it is very expensive to go there.'' Winning Partners has run once since his narrow defeat of English filly Marina Park in the International Bowl, running third to Happy Guy and Concert King at level weights in the Centenary Cup down the straight 1,000 metres. His trackwork since hasn't appeared to be of the same outstanding quality of his work leading into the Bowl. Meanwhile, John Moore stressed that he had yet to even draw up a short-list of jockeys to replace Johnny Marshall who has decided to move to David Hill. Moore said: ''I fully expected the move after John won so well on River Verdon. ''But even so I haven't thought about who will replace him. I certainly haven't contacted either Damien Oliver or Brian York who some people are linking me with.'' Oliver, due here in a fortnight on a one-month licence, yesterday lost his appeal against a riding suspension in Australia and will not be able to ride here until May 15 in the Champions and Chater Cup meeting.