Usually, when you keep a clean sheet on the road against one of the division’s better sides, that often means your defence has done a pretty solid job. But those who tuned in to watch Rangers grind out an unconvincing 0-0 draw away to Heart of Midlothian on Saturday afternoon – their Premiership title challenge beginning with a whimper rather than a roar – will know that a shutting out of Steven Naismith’s dangerous frontline was very much a one-man effort. Reigning Player of the Year Jack Butland, as he did throughout last term, came to Rangers’ rescue on numerous occasions. He almost single-…