Derek Ferguson has delivered a scathing rant on one Rangers star who has been offering ‘absolutely nothing’ over the last five or six games. The Light Blues have let their standards slip at the most crucial of times and it has handed the initiative to Celtic in the Scottish Premiership title race. Rangers showed supreme mental fortitude in the Old Firm derby draw with Celtic recently as they fought from 2-0 and 3-2 down to secure a point at Ibrox. That kept them in the driving seat for a first league trophy since 2021. But harrowing performances against Ross County and Dundee followed and thos…