Jesse Marsch: “It’s an important game in many of our guys’ lives.” (Brad Rempel/USA TODAY Sports)

CINCINNATI — How big a deal is Tuesday night’s Lamar Hunt/U.S. Open Cup semifinal for the Red Bulls?

A big deal, a really big deal when they take on FC Cincinnati.

Before the Red Bulls walked out onto the Red Bull Arena pitch for their game against Orlando City SC Saturday night, head coach Jesse Marsch did some long-distance scouting. He looked at Cincy’s Starting XI for its United Soccer League match against Louisville City FC.

Marsch needed to know what his foes were planning beyond the game, which turned out to be a 5-0 defeat at Louisville.

“They played a lot of their regulars,” he said after New York’s 3-1 win. “They sat a couple of guys. They rotate a lot on their team. It will be a little bit of a guessing game what their lineup would be.”

During the RBA game, Marsch made three substitutions with the Open Cup encounter in mind. He pulled striker Bradley Wright-Phillips for Gonzalo Veron in the 68th minute, center back Damien Perrinell for Aurelien Collin in the 76th minute and Kemar Lawrence for Connor Lade in the 82nd minute.

“We needed to find ways to get a lead, and then see if we could make adjustments to get through the game,” Marsch said, “and also, make sure that we were going to have our legs on Tuesday.”

FC Cincinnati is the Cinderella team of the 2017 Open Cup, having eliminated Major League Soccer sides Columbus Crew SC and the Chicago Fire in the fourth and fifth rounds, respectively, before edging the Miami FC (North American Soccer League), 1-0, in the quarterfinals.

The hosts will be without its top scorer Djiby Fall, who is suspended due to yellow-card accumulation.

The Red Bulls still are not taking Cincy lightly for its Nippert Stadium match.

“You know, everyone around here is really excited for Tuesday,” Marsch said. “Really excited for a big game against a club and a team we don’t really know, and it’s going to be in a stadium that there’s going to be more energy in that stadium than maybe we felt all year, and a team that’s playing in the most important game in many of their lives.

“So, and to be fair, it’s an important game in many of our guys’ lives. So, it sets up to be a great match and a fun match and one that we’re going to take very seriously and we know is very important.”

Ditto for goalkeeper Luis Robles, who understood that games like this don’t come around too often — for both teams.

The Red Bulls performed in one final — losing to the Fire in 2003. Cincinnati is looking to become the first lower-division team since the Charleston Battery to advance to the final. In 2008, Charleston finished runner-up to D.C. United.

“It’s a huge game for this organization,” Robles said. “It’s a huge game for this group of guys,” he said. “So, we know that recovery is important right now. … We know, with a sold-out crowd, they’re going to be up for it. So, we’re not taking this game lightly and we expect the best available eleven from them and we expect them to really bring the game to us.”