Philippe Clement claims that the Ross County defeat was the worst performance of his Rangers tenure to date. It’s been six months since Big Phil took the reins at Ibrox and in that time the Belgian manager has lifted a League Cup with a treble tilt very much set to go down to the wire. But as Rangers handed Celtic the Scottish Premiership title advantage with a 3-2 defeat in Dingwall, you’ll forgive Rangers fans for fearing the worst in the club’s title challenge. With Philippe Clement grilled on his side’s title credentials, the Rangers manager addressed a brief press conference after the def…