Alexander Romanov signed an eight-year, $50 million contract extension last summer that suggests the Islanders plan to have the 26-year-old defenseman in their top four for a long period of time. The question going into this offseason is whether the Islanders, after a season in which Romanov played 15 ineffective games and then had his season cut short by injury, are still comfortable assuming that will be the case? The answer is going to play heavily into what kind of moves Mathieu Darche can make. Darche, we know, does not love the upcoming free-agency class, and the Islanders, relatively speaking, are not swimming in cash this offseason anyway. If a big opportunity presents itself, chances are it will be via some kind of trade. So let’s play process of elimination. The Islanders are considered very unlikely to trade Cal Ritchie, Victor Eklund or Kashawn Aitcheson, all players who should be considered part of the next core that will contend for a Stanley Cup.…