Mike GreenawayThe Blitzboks lost their fifth-place play-off against Argentina in the Singapore Sevens to end a weekend when they did plenty of good but ultimately failed when it mattered most.The South Africans enjoyed an unbeaten run in their three pool matches but lost both of their play-offs, going down by 29-24 to Australia in the quarter-final on Saturday – with their opponents clinching the victory with a golden try in extra-time – before Sunday morning’s second successive close result against Argentina (14-10).That result earned the South Americans the World Series title. The…