The Italian striker joined the Hammers on loan this summer, with the deal automatically becoming permanent on his 15 appearance. That transfer would be worth £17.5m plus bonuses to Juventus who have already budgeted for that money to pay for their Juan Cuadrado transfer deal.
Italian website Calciomercato.com says the threshold was set deliberately low in order to virtually guarantee that Zaza would move to West Ham permanently.
The website quite rightly speculates that West Ham are now getting cold feet on the striker who has so far made five appearances. West Ham are thought to have paid a £4.2m season long deal although it is not known whether that includes his £70,000 per week wages.