Even though the Union play in Chester and the Red Bulls play in Harrison, N.J., it's still Philadelphia vs. New York to all concerned.
And at least from the Union's perspective, less than three years is more than enough to stir this rivalry.
"Regardless how many years we've been around, it's Philly and New York, and nobody in Philly likes any teams in New York, and that is definitely how it goes with the Union and Red Bulls," Union defender Sheanon Williams said.
Welcome to Philadelphia, er . . . Chester, Red Bulls.
Maybe that was just the overexuberant opinion of one player, so it may be important to get a more refined view of this rivalry from Union assistant coach John Hackworth.
Lo and behold, he had a similar take.
"I don't think they like us and I don't think we like them," Hackworth said of the Red Bulls. "What more do you need? They are close to us."
Close in proximity, but right now, not in the MLS standings.
"They are ahead of us [in the standings], so we are very hungry to get a result on Sunday," Hackworth said.
Actually, the Union would be hungry for a result if they were playing a men's league team from South Jersey.
This was not the start the Union envisioned. Granted, the schedule has been difficult, but in MLS, where many teams are evenly matched, there are few laughers.
And even though the Union may not profess much affection for the Red Bulls, there is obviously respect.
"They're coming off three games with really good results," Hackworth said. "They've got some players back now. This is going to be a big challenge, but a game I think we're ready for."
How can the Union not be ready for the Red Bulls?
These two ended their regular season against each other last year, with the Red Bulls earning a 1-0 home victory.
Part of what makes a rivalry is beating a team in must-win settings. The Union have played just under a quarter of their schedule, so it would be a stretch to call Sunday a must-win (or must-tie) situation, but it's not too far from that.
The Union have lost consecutive MLS games, while the Red Bulls have won their last three games by 1-0 scores.
One team has the momentum, the other has the home crowd.
Right now, the momentum seems to be the better option, although that's subject to change. The Union were 7-1-9 at home during last year's regular season. This year, they are 1-2-1.
"New York will definitely be a tough opponent," Williams said. "We are at home, but we need to play like we're at home and need to make [PPL Park] back into the fortress it once was."
Like all the way back to last year, when the Union beat the Red Bulls, 1-0, on April 9 in Chester. Even back then, the dislike for the Red Bulls had already brewed into a rivalry that didn't need much more than a road map to get started.
Contact Marc Narducci at 856,779-3225, firstname.lastname@example.org or follow on Twitter @sjnard.