The rivalry was stimulated from matches of consequence. And it was further fueled by an exchange of words between Sporting Kansas City and Real Salt Lake players over the past two seasons.
While the two teams' most notable meeting came in the 2013 MLS Cup final, a bevy of the encores have offered notable repercussions, too. The latest chapter Sunday presented Sporting KC with an opportunity to clinch its spot in the MLS postseason for the sixth consecutive year.
Instead, that will have to wait until the final week of the season.
Sporting KC and Real Salt Lake played to a 0-0 draw Sunday, muddling the playoff picture further as the league heads into its Decision Day next weekend.
Sporting KC remained in the sixth and final playoff spot in the Western Conference, and it can secure its berth with a victory against San Jose next Sunday.
"It's better to be in that position that being on the outside and needing help," coach Peter Vermes said in a phone interview.
"I thought the team from start to finish was fantastic. We easily deserved a point."
And perhaps more.
The game hinged on a penalty kick that wasn't given in the 78th minute. Sporting KC midfielder Benny Feilhaber appeared to be tackled in the box, but referee Ismail Elfath kept his whistle silent.
"You can't miss that. You can't miss that penalty. How do you miss it? I mean, honestly, how do you miss that?" Vermes said. "I actually think (Elfath) did a really good job in the game, but I don't know how you miss that."
A whistle certainly could have significantly bolstered Sporting Kansas City's playoff positioning, but the draw will add more drama to the final weekend of the MLS regular season.
Portland moved into a tie with Sporting KC for the final playoff spot after it defeated Colorado on Sunday. Sporting KC owns the tiebreaker with its minus-1 goal differential this season compared to the minus-2 from Portland.
Fourth-place Real Salt Lake and fifth-place Seattle will also match up on the final weekend, and neither have clinched a postseason berth yet.
It will be the second straight season in which Sporting Kansas City's playoff hopes will rest on the regular-season finale. A year ago, the club earned its place with a victory against the LA Galaxy.
For the time being, one of the best defensive efforts of the season kept Sporting KC on the right side of the red line. Tim Melia made four saves for the shutout. Matt Besler returned to anchor the back line after a much-publicized two-game absence due to a coaching staff's decision.
"I thought Matt Besler had one of his better performances in a long time," Vermes said. "He was fantastic in the game."
Melia was equally impressive in goal, and he was matched by his counterpart, RSL keeper Nick Rimando, who made five saves. Three of those came against Sporting KC forward Dom Dwyer, who provided the team's best scoring opportunities.
All went for naught.
"As you saw today, we didn't come here to just hang out — we came here to play," Vermes said. "We went after the game from the opening whistle. For us, it obviously was a big game, and at the same time, Sunday will be, too."