Eli Manning has yet to see Brandon Marshall on the field, but that hasn’t stopped him from imagining what it will be like.

“That’s a good visual in my mind,” Manning said Friday of the 6-4, 230-pound Marshall, the newest addition to the Giants’ wide receiver group. “Odell [Beckham Jr.] over here, Brandon Marshall over there. That seems right.”

Manning discussed the signing during an hour-long Q&A at a luncheon for the Long Island Association, the region’s largest business group. He and brother Peyton Manning were the guest speakers at the event.

“I’m excited,” Eli Manning said of the signing. “I talked to him the other day. He’s a tremendous player. A big target.”

Manning wasn’t the only one excited. A room filled with 1,200 cheered each video clip of Giants Super Bowl exploits and mentions of Big Blue triumphs. This might have been the only banquet Peyton ever attended in which he felt like the younger brother, the sub-attraction.

Even Msg. Brian McNamara, delivering the invocation, played to the pro-Giants crowd.

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“And Lord,” he ended his prayer, “if you can see fit to give Eli an All-Pro left tackle, that would be nice, too.”

The Mannings discussed everything from growing up in New Orleans (“a very normal childhood,” Eli said) to their NFL games against each other (“pretty miserable” for their parents, Peyton said) to Eli’s home in Quogue. “We love it out here,” Eli said of Long Island.

There was even some Jets talk, mostly regarding the number one pick in the 1997 draft — when Peyton decided to remain in college and not enter the NFL as the presumed pick of the Jets — as well as Peyton’s brief free agency, when he had discussions with the Jets before signing with the Broncos.

Peyton said he stays in touch with Bill Parcells, then the head coach and general manager of the Jets, who would have selected him in 1997. They met in Florida last week, when Peyton “picked his brain on the business side of football.”

As for his post-retirement plans, Peyton said he has not made any decisions. Eli called him “an embarrassment” for being the only member of the family over 40 years old and unemployed.

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Eli also spoke about being drafted by the Chargers and traded to the Giants, his relationship with Tom Coughlin, and 8-year-old fans in Philadelphia who “say some things about my mom.”

The LIA has attracted a number of big-name speakers in the past — from former Presidents Bill Clinton, George H.W. Bush and George W. Bush to politicians such as Mitt Romney and Colin Powell. It also has featured local sports personalities such as Derek Jeter (who spoke at the luncheon in 2015), Joe Torre, Phil Simms, Rex Ryan and Boomer Esiason.

Peyton Manning said his one regret in his NFL career was not being able to break Brett Favre’s record of 297 consecutive regular-season starts. Peyton, who started 208 straight games, believes Eli will do that, though. The 36-year-old has never missed a start, a streak of 199 regular-season games.

“I don’t think Eli would tell the Maras and the Tisches this,” Peyton said of the Giants’ owners, “but he would play for free.”