Play a team in your own division three times in a season, and things get that way.
That's only the start, though.
Add in the 95-mile trek up or down the New Jersey Turnpike and the fact that Sunday's game will be the eighth between the teams in the last three seasons, and this rivalry can get downright nasty.
"There's a strong dislike for one another," Giants guard Chris Snee said. "Anytime you get a chance to knock out a divisional opponent, one you don't like, you get geeked up for these challenges. I think both sides would agree that to knock the other out would make the other one happy."
There is another element that will add to the intensity. The NFC semifinal at Giants Stadium matches the defending Super Bowl champions against the team that many think will be the 2009 version of the New York Giants.
"I don't think anybody has to do anything to get up for this game," New York cornerback Corey Webster said. "I think it is already built up. Everybody knows what is at stake. I just think every team is going to be prepared and ready to go and they are going to be very excited and our guys are going to be up for the challenge this weekend."
Of the seven previous games during the last three seasons, only two have been decided by more than 10 points, with the largest margin being 14.
The two games this season were decided by a combined 11 points. New York (12-4) won 36-31 in Philadelphia and the Eagles (10-6-1) returned the favor at Giants Stadium 20-14 on Dec. 7.
"I think the guys all know each other and everybody knows each other's number, jersey number, and all that bit," Eagles coach Andy Reid said. "But every game is different and if you come in saying you know the New York Giants, I think you make a huge mistake in the process of getting ready to play them."
While the scores were close, the statistics weren't. The Giants dominated time of possession (39:10) and total yards (410) in the first game, and the Eagles had the advantage in the second, holding the ball for almost 35 minutes, while outgaining New York 331-211.
Eagles safety Brian Dawkins said the Giants have always been a rival for him.
"I've always had respect for them," Dawkins said. "I'm not cushy with them, but I've always respected this team. It's always been a physical battle with this team. Every once in a game it's been a blowout, but, for the most part, it's usually some grind-out, close, defensive battle with this team. Since I've been here, this has been, to me, my biggest rivalry game."
The Giants come in as somewhat of a question mark. Tom Coughlin's team won 11 of its first 12 games, and then lost three of four in December. Their only win was an overtime decision against Carolina that wrapped up the conference's No. 1 seed in the next to last week of the regular season.
Adding to the team's woes was the season-ending suspension of Plaxico Burress in early December after the receiver accidentally shot himself in the thigh at a New York City nightclub.
Burress has been very successful against the Eagles since joining the Giants in 2005. A downfield threat, he forced Philadelphia to keep a safety deep.
Without him, the Eagles were able to play the safety closer to the line of scrimmage in the last game and they held New York's league-leading rushing game (157.4) yards to 88 yards.
Giants leading rusher Brandon Jacobs aggravated an injury to his left knee in the game and he did not return for the second half.
Reid said that the running game is only half of the Giants' package. He noted quarterback Eli Manning, the Super Bowl MVP, had his best season, Kevin Boss has developed into a good young tight end and that Amani Toomer, Domenik Hixon and Steve Smith can be formidable receivers.
Hixon, who has replaced Burress in the starting lineup, dropped a 50-yard pass in the second quarter of the last game with the Eagles ahead 3-0. If he catches it, who knows how that changes the contest?
"I know people look at the run game and say, 'Hey, they are the best run team in the National Football League,"' Reid said. "Well, they sure are. They are a tremendous run team, but there is also another half of that you have to prepare for that makes it a difficult process to go through. It makes them a very good team."
Defensively, the Giants will have to find a way to slow down quarterback Donovan McNabb and halfback Brian Westbrook, who scored on a 40-yard pass and a 30-yard run in the last meeting. Westbrook also turned a screen pass into a game-deciding 71-yard touchdown in a 26-14 win over the Minnesota Vikings last weekend in the playoff opener.
The win was the fifth in six games for the Eagles, who are the conference's hottest team.
McNabb wanted no part in a comparison between the Eagles of this year and last year's Giants, who got hot late in the season en route to the title.
"It's easy to say that at this point," McNabb said. "They went on and won the Super Bowl. We are just in the second round. Maybe as we continue on, maybe. But we just want to kind of be the Eagles of 2009. I mean, it's easy to sit back from afar and say that, but I don't see it right now."
What both teams will agree upon is that Sunday ought to be a great game.
"There's excitement and a lot of anticipation, but mostly, really it's exciting," Giants defensive end Mathias Kiwanuka said. "This is where you want to be. I mean, there's not a lot of teams left. Everybody started with the same mentality. We all have friends and former teammates around the league and they all say the same thing: 'I'd much rather be in your shoes than out there on the greatest beach in the world."'