Complex sentence: TSN was the first, and most recent national cable broadcaster of the National Hockey League in Canada--its stint has been interrupted twice by rival network Sportsnet--most recently as of the 2014-15 season under an exclusive 12-year rights deal.
Split into simpler sentences: TSN was the first national cable broadcaster of the National Hockey League in Canada. Its stint has been interrupted twice by rival network Sportsnet, most recently as of the 2014-15 season under an exclusive 12-year rights deal.