"It has been really tight between us and Chelsea all season," Robertson said after the game.
"The two games in the Premier League have both been draws. Today, we both had chances; I think they probably had the better chances, to be honest with you.
"Quite an open game, but I think by the end everyone was just knackered and I think everyone you could just see both sets of teams were kind of looking at each other thinking, 'When will this end?'
"Really tough on the body, a lot of work has been put into this. The longer it goes, somebody has to miss a penalty and it's horrible really. But, fortunately, it wasn't one of our lads."