It was only mid-October, but one could have mistaken the energy in Madison Square Garden Saturday night as the Knicks played their preseason home finale against the Boston Celtics for that of a late-May playoff game.

Fans throughout the arena reacted excitedly and loudly as some of the Knicks’ young players, trying to make a strong impression on the team’s key decision makers, fought hard to pull out a win. They came up short, losing 119-107, but the atmosphere may have foreshadowed what the Garden will feel like if the Knicks can transform into a playoff contender.

There was no more electrifying arena in basketball when the Knicks were regularly challenging for the Atlantic Division and Eastern Conference titles in the 90s, making it all the way to the NBA Finals in 1994 and 1999, defeated 4-3 and 4-1, respectively, by the Houston Rockets and San Antonio Spurs. But hard times over the better part of the past 15 seasons have dampened the dynamism if not the hope of the collective fan base, who long for the good old days.

But perhaps a player such as 22-year-old, 6-11, 240-pound rookie Guillermo “Willy” Hernangomez from Spain, who has shown a nice combination of smarts, athleticism and skill, will emerge as a solid contributor this season and moving forward to help the Knicks’ cornerstone players Carmelo Anthony and Kristaps Porzingis rebuild the franchise into a consistent winner.

“He does a lot of good things for us,” said Knicks head coach Jeff Hornacek after Hernangomez, who was originally drafted by the Philadelphia 76ers in the second round (35th overall) and traded to the Knicks, scored 12 points and had 12 rebounds in 24 minutes versus the Celtics.

“You saw some of his abilities in the passing. He makes nice passes. He’ll learn the quickness of guys when he gets [a] rebound inside to get it up strong.”

The Knicks met up with the Celtics last night (Wednesday) in Boston and will conclude their preseason schedule against the Nets in Brooklyn tonight. Then the games really begin to matter, starting with LeBron James and the defending NBA champion Cleveland Cavaliers on the road next Tuesday.

Early tests such as the Cavaliers won’t be the definitive measure of how the Knicks’ season will evolve. It will take a while for the players to grasp Hornacek’s system and learn each other’s tendencies. But it is the opener, which is always symbolically significant.

No doubt, the fans occupying the Garden Saturday will be ready.