Nike shares tumble as it loses ground to upstart rivals

Nike had said it expects a surprise 10% drop in quarterly revenue, as it faces growing competition from newer rivals such as On and Hoka.The news sent Nike shares plunging more than 12% in after hours trading, which could mean a loss of $15bn in market value if the losses hold on Friday.The world's largest sportswear company also told investors it is facing weakening demand in international markets, including in…