When the New York Islanders announced their upcoming move to Brooklyn last October, New York City mayor Michael Bloomberg stated, “Who said the rivalry between the Rangers and the Islanders couldn’t get any bigger? Well, it just did.”

Actually, the rivalry is already bigger, even before the Islanders take their first skate in Barclays Center. Because this Saturday, the Rangers and Islanders will square off at Nassau Coliseum with more than just bragging rights on the line.

It’s a scenario few could have predicted at the beginning of the 2012 -2013 season. The Blueshirts were supposed to run roughshod on the Eastern Conference, and contend for the Atlantic Division crown. The Islanders were supposed to be the promising team that was still a few years away from entering the playoff conversation.

Yet entering action on Friday, the Islanders are two points ahead of the Rangers (although the Blueshirts have one game in hand). It’s one of the few times over the last two decades that the Blueshirts and the Nassaumen have been in this position.

Sure, the two squads faced off in the first round of the 1994 Stanley Cup Playoffs — the last time these rivals have played each other in the postseason. But that series ended in a 4-0 sweep, as the top-seeded Rangers outscored the eighth-seeded Isles 22-3 in the four contests.

There were other playoff races, during the 2002-03 and the 2006-07 season, where the rivals were both in playoff contention. In fact, the contest on Saturday will be the most meaningful game — in terms of playoff positioning — the Rangers and Islanders have played since April 3, 2007, when an Islanders shootout win ultimately led to them clinching a playoff berth on the season’s final day.

The truth is that the rivalry slowly faded in the last two decades. Since the Rangers faced the Islanders last in the playoffs, they squared off against the Devils five times, the Penguins twice, and the Flyers twice in the playoffs. In addition, the Rangers and Flyers essentially had a “play-in” game on the final day of the 2009-10 regular season.

What’s more, during the three consecutive years that the Islanders made the playoffs (from 2001-02 to 2003-04), the Blueshirts missed the postseason.

All things being equal, the Islanders are the Rangers’ biggest rival, and vice versa. When playoff implications are at stake, that statement is magnified, both on the ice and in the stands.

After the Islanders’ 4-1 victory over the Flyers last Tuesday, the crowd chanted, “We Want Playoffs.” With the Blueshirts entering the Coliseum Saturday, the chants will be louder from Islanders and Rangers fans alike.

Who said the rivalry between the Islanders and the Rangers couldn’t get any bigger before the Isles moved to the five boroughs? It already has.