That visitor was Peyton Manning, Eli's older brother who is enjoying his retirement after 17 years in the NFL.
The older Manning didn't speak to the media, but his brother revealed that Peyton took some time to watch film with the Giants quarterbacks during their meetings and share some feedback.
"It was good to have him here. I hadn't seen him in a while," Eli Manning said. "He has something to do (Wednesday) so he popped in and sat in on a few meetings with us today. Just good to catch up. I'll get some time with him later."
The Giants are just now getting into their installations for their game Sunday at Heinz Field against the Steelers, a team they only see once every four years.
Peyton Manning, on the other hand, has a bit more experience dealing with the Steelers, most recently a 2015 playoff game in which he completed 21 of 37 passes for 222 yards in a 23-16 win in the AFC divisional playoffs last year.
Eli Manning didn't reveal what tips Peyton might have shared about the Steelers' defense, but he did smile when recalling how his brother seemed to slip right back into his element during his visit.
"I think when he gets in this environment, he was kind of drilling the coaches his own questions. I know he liked being in there and doing a little install on Pittsburgh," Manning said.
"I'm sure he misses that environment. Just the game plan, how you're going to do things, how you're going to deal with protections, how you're going to pick things up. Just really getting back into that flow of things, I'm sure, is a little reminder of how special it is to be in this situation."
And if the tips do pay off, might Peyton Manning have a future in coaching?
"You'd have to ask him," Eli said with a grin.
--When the Giants drafted wide receiver Sterling Shepard in the second round, they envisioned him as being a part of the team's long-term plans.
They still do, even though the rookie didn't have a single pass attempt thrown his way last week.
"I apologized for not getting him a catch," said Manning, putting to rest any theories that he was ignoring the rookie in last week's win over the Browns.
"We need to get him the ball and get him catches. That's just the way the day kind of went. He's done a good job all year and we have to get him involved in the offense."
The reason for Shepard not seeing any pass targets, according to Manning, was all in the coverages the Browns were showing.
"What we were trying to do and the coverages that we were getting, we had other guys that were the primary," he said. "We just didn't get it down to him."
Shepard, out of Oklahoma, has primarily lined up in the slot for the Giants this season. He's caught 44 of 72 pass targets for 476 yards and five touchdowns, three of which have come since the Giants returned from their Week 8 bye.
The rookie has one 100-yard receiving performance to date, that coming back in Week 2 when he torched the New Orleans Saints for 117 yards.
Since returning from the bye, he's had to give up some of his slot snaps to Odell Beckham Jr., whom the coaches have been trying to move around to get the favorable matchups.
Shepard insisted that his confidence wasn't shaken by the lack of targets last week and expressed confidence that he'll see many more targets as the Giants continue their quest for their first postseason berth since 2011.
"I know that I am going to be able to touch the ball, especially next game and moving forward. That is why I am not making a big deal about it," Shepard said.
"It was kind of weird because I usually get that first touch and get hit the first time and I hadn't had that feeling and I was like, 'Ah.' But I know it is going to be alright and we came out with the 'W,' so that is all that matters at the end of the day."
--Kicker Robbie Gould's Giants career hasn't quite gotten off to the start for which he was hoping.
In his last two games, Gould has missed three PATs which fortunately didn't come back to haunt New York, but which were nonetheless concerning.
So what exactly has happened to turn the PATs into an adventure?
"I just missed it," Gould said of his latest missed PAT which came last week against the Browns. "The timing on my end was a little off, and I just pushed it right."
Whereas two weeks ago when Gould missed two PATs affected by sudden gusts of wind, his miss last week in a calmer weather environment is inexcusable.
"I've got to make them. The team's been doing really well, getting the ball in the end zone. Points are precious in the league, and I get that. I know I can perform better than what I'm performing, and I need to do it, and do it quick."
The Giants are not quite ready to give up on Gould, who was signed Oct. 22 to replace Josh Brown as their kicker.
"I'm not worried about it," Gould said when asked about his job security. "I'm worried about doing my job, and doing it to the best of my ability. Last week, I had a good game except for the extra point. Obviously, that's frustrating. But at the end of the day, it comes down to making kicks, and I've got to do that."
To be fair, Gould did miss the first six weeks of the season after his 11-year career with the Chicago Bears came to an end after training camp concluded.
Since signing with the Giants, he's made 13 of 16 PATs and both of his field goal attempts. He believes that as he continues to work with his new battery mates, long snapper Zak DeOssie and holder Brad Wing, these early rough patches will eventually smooth out.
"You can't have (missed opportunities), especially when you're trying to make a playoff run," he said. "These games that we have coming up are big games. I know what's at stake, I know I've got to go out and do my job. I want to do it for my teammates and the organization. It comes down to me just doing my job."
Wing said he doesn't view Gould as being in a slump right now, but did add that the most important thing he and the rest of the team could do to help Gould accelerate his acclimation to the Northeast winds is to be supportive.
"It's just being there for guys; it's not just having them comfortable on the field, but also off the field," said Wing, who also revealed that the kicking battery has been getting extra work inside MetLife Stadium during the week.
"He's a good guy. He's come in and earned the respect from guys very quick and our job is to make him comfortable because he knows how to kick."