After all the pre-match build-up, today is finally here. Celtic take on Rangers at Ibrox in the biggest Glasgow Derby of the season this afternoon. With the top of the table so tight, any slipup by any team will give the opposition a huge psychological advantage heading into the top-six split. Now I am fully aware that Celtic have still to face St Mirren at Celtic Park and Aberdeen at Pittodrie before then but you would have to concede that whilst today is far from being a title decider, it will give whoever wins it a huge lift heading into the final stages of the season. At one point, Celtic …