Playing on the top line against an Ottawa Senators squad with many of their best talent, Nick Robertson’s offensive explosion and growing confidence is exactly what the Maple Leafs wanted. BELLEVILLE, Ont. — Toronto Maple Leafs head coach Sheldon Keefe always knew Nick Robertson had it in him. That’s why when the club had called up American forward in the past, they would often slot him in as a second-line left winger. And while he didn’t produce the results they had been looking for in the past, Robertson made the most of his opportunity on Friday. Placed on the top…