Fans cheer in Game Three of the Semifinals of the...

Fans cheer in Game Three of the Semifinals of the 2021 Stanley Cup Playoffs between the New York Islanders and the Tampa Bay Lightning at Nassau Coliseum on Thursday, June 17, 2021 in Uniondale, New York. Credit: Jim McIsaac

The Islanders played their biggest game at Nassau Coliseum since 1984 on Saturday night, which sounds like a big deal until you consider what was going on about 23 miles to the west.

That was where the Nets were hosting the Bucks in Game 7 of a second-round NBA playoff series, which only was the biggest sports event held in Brooklyn since Game 7 of the 1956 World Series.

So to review: One arena was hosting its most important hockey game since the first Reagan Administration, and the other was hosting its borough’s most important game of any kind since the first Eisenhower Administration.

But that is not what made the confluence of events on Saturday so cool.

(Well, actually, it was not so cool that the leagues and their TV partners gave us simultaneous Islanders and Nets playoff games Tuesday, Thursday and Saturday. But that is another story.)

The historical wrinkle was that the two franchises have a long, entwined history, which some of the time would have meant that a night such as Saturday was a logistical impossibility.

When the Islanders began playing at the Coliseum in the autumn of 1972, the arena already had been christened as a sports venue when the Nets hosted the Pittsburgh Condors there on Feb. 11, 1972.

Fans cheer as Mike James #55 of the Brooklyn Nets...

Fans cheer as Mike James #55 of the Brooklyn Nets \hb against the Milwaukee Bucks in Game One of the Second Round of the 2021 NBA Playoffs at Barclays Center in Brooklyn, NY on Saturday, June 5, 2021. Credit: Steven Ryan

Rick Barry scored 45 points and Billy Paultz 26 in the Nets’ 129-121 win. Attendance was 7,892, and not because of pandemic capacity restrictions.

Roy Boe owned pieces of both franchises and continued to do so through the Nets’ ABA championship years of 1974 and ’76.

So the Islanders and Nets obviously could not host playoff games at the same time in that era. But there still were conflicts of the sort that has gone on this past week.

When the Nets and Nuggets met in the 1976 ABA Finals, their first three games were on the same days – May 1, 4 and 6 – as Islanders playoff games against the Canadiens.

But the Nets started with two games on the road, then came home for Game 3. The Islanders were at home for the first two days, then on the road for the third.

The Nets left Long Island for New Jersey in 1977 and moved to Brooklyn in 2012. In 2015, the Islanders followed them there, and for parts of five seasons they again were co-tenants.

The Islanders last played a home game at Barclays in March of 2020, and this autumn they will move to UBS Arena at Belmont Park, about nine miles from the Barclays Center.

There is one other thing the Islanders and Nets have in common, which is that they are not the Rangers or Knicks, and thus forever viewed as being in the shadows of their more established counterparts.

But all that has changed late this spring, with the teams that shared both the Coliseum and Barclays Center having gone into Saturday night looking continue rocking their respective barns, while the Rangers and Knicks are long gone.

The Islanders needed a victory in Game 4 against the Lightning to ensure it would not be the last game they played the Coliseum.

The last time the building hosted an NHL semifinal was in 1993, when the Canadiens won the first two games in Montreal, then won Game 3 at the Coliseum. The Islanders saved face by winning Game 4 before losing the series in five.

But neither of the games at the Coliseum in that series could quite match what the Islanders and Lightning were facing on Saturday night.

The Islanders have reached the NHL final four against Tampa Bay for the second year in a row, but last year that drama unfolded in an empty arena in Edmonton.

A full arena on Long Island was much better, with the added tension that came from it perhaps being the last game there forever.

Some fans no doubt would check their phones during TV timeouts and intermissions to see what was going on in Brooklyn.

And vice versa.