Nick Rimando and Matt Pickens take the field in 2011

For all the years of hostility between the Colorado Rapids and Real Salt Lake in the Rocky Mountain Cup, the one moment that perhaps best defines the teams’ relationship is the one at least some people would love to leave in the past.

That moment – which came at the end of a particularly heated match at Rice-Eccles Stadium on Sept. 2, 2006 – pitted longtime Rapids captain Pablo Mastroeni against RSL’s mild-mannered then-owner Dave Checketts. The two engaged in a heated exchange on the field following the Rapids’ 1-0 win, and after Mastroeni removed his shirt, stuffed it down his pants and gestured towards the fans.

Mastroeni – who has suited up against Real Salt Lake 14 times since the rivalry was founded in 2005 – declined to talk about the episode recently in preparations for the teams’ latest entanglement at Rio Tinto Stadium on Saturday (6 pm ET; MLS Live), but there’s no denying that the altercation was a watershed moment for a rivalry that has since cleaned up its act, but hasn’t lost any of the passion.

“I was walking back to the locker room, and all of a sudden all these players started running back onto the field,” former RSL midfielder Andy Williams (right, No. 77) said of the 2007 incident. “There was a huge crowd around Pablo and Dave yelling at each other, and then later everyone’s looking at all the photos of Pablo with the shirt down his pants.

“That blew everything up. That was the first time I’d ever seen something like that. Everything really traces back to that point."

Rocky Mountain Cup rivalry between Colorado Rapids, Real Salt Lake still about altitude, attitude -

It’s somewhat surprising tensions have never quite boiled like that during 17 matches since. Take into consideration that both Kyle Beckerman and Chris Wingert jumped across state lines from Denver in 2007 and playoff berths were won by RSL at Colorado’s expense during season finales in both 2008 and '09, and the series has provided Major League Soccer with some of the best storylines of any rivalry over the past five years.

“For us, it is [the best rivalry],” Mastroeni said. “You step in that stadium, you know what you’re about to encounter – some fans that are going to be over the top and make your day warming up during the game and postgame as miserable as they can.”

Unfortunately for Rapids fans, the series has been decidedly one-sided since Real Salt Lake truly came of age in 2007. RSL have won each of the past six incarnations of the series since head coach Jason Kreis went head-hunting for Beckerman, and they’ve absolutely dominated each of the past two years, outscoring the Rapids by a combined score of 10-4 across four games.

The last two years’ futility comes after devastating blows in 2008 and '09, when RSL not only clinched the Cup but also earned MLS postseason berths with season-finale results against the Rapids: a 1-1 draw that eliminated Colorado in Denver in 2008, and a 3-0 romp at Rio Tinto that kick started RSL’s unlikely run to their first MLS Cup in franchise history.

Add in two dramatic results inside a month in 2010 – a last-second header that somehow kept alive RSL's unbeaten streak at Rio Tinto, and then a complete collapse by the Rapids back in Commerce City with the Cup on the line – and RSL have used the Rapids rivlary as something of a launching point for their success.

“Every time it seems like we go at these guys, and that’s the turning point in the season,” said defender Nat Borchers, a native of Pueblo, Colo., who joined RSL in 2008 after once serving as an anchor for the Rapids’ defense from 2003-06. “Colorado have always had guys that are very tough to play against, and their fans are as tough as any to play in front. Their fans have a huge chip on their shoulders for all the Rocky Mountain Cups we’ve won and what we’ve done in the past.”

Rocky Mountain Cup rivalry between Colorado Rapids, Real Salt Lake still about altitude, attitude -

Borchers is one of 12 players who have suited up on both sides of the rivalry, but no one has been more successful in the series than Beckerman (right, with the Rapids in 2007). He’s never lost the series in eight years, having won the trophy each of the past six seasons with RSL and each of the first two years while with Colorado.

Borchers and Wingert are perfect in the series too, thanks to six wins with RSL and one with the Rapids before heading west of the Rocky Mountains.

They’re also part of a dying breed of players who’s seen the ups and downs of the series in years past, thanks in large part to big offseason moves for both Colorado and Real Salt Lake that jettisoned players like Conor Casey, Omar Cummings, Jeff Larentowicz, Jámison Olave, Fabián Espíndola and Will Johnson.

But the Rapids still boast the likes of Mastroeni, goalkeeper Matt Pickens and defenders Drew Moor and Marvell Wynne, while Beckerman, goalkeeper Nick Rimando and striker Álvaro Saborío are all healthy and eyeing another round of a rivalry like few others in the league.

“There’s some other atmospheres in MLS – Seattle, Portland – that are fantastic, but for some reason when we go to Salt Lake, that place is as loud as any place we play,” Moor said. “They’re certainly saying stuff that you wonder how they found out info about you. It makes it fun. It’s a healthy respect, we enjoy going there to play, I’m sure they enjoy coming here to play. It’s a great rivalry.”