To have a fierce rivalry you usually need healthy, or sometimes bordering on unhealthy, doses of three things - proximity, history and animosity.
The Portland Timbers-Seattle Sounders FC rivalry, which has become the marquee duel in Major League Soccer, certainly fits the bill on all three counts.
Fans in Tucson will get a chance to see that rivalry in person today, albeit in a somewhat less-intense preseason mode, when the teams square off in a MLS Desert Friendly at Kino Sports Complex North Field No. 5 at 10:30 a.m.
"You're going to have a lot of people (today) - with the Timbers Army and the ECS (Emerald City Supporters), it's two huge supporters groups," said Tom Long, a Timbers fan who moved from Portland to Show Low last May and attended Portland's match against Sporting Kansas City at Kino on Friday.
Portland midfielder Darlington Nagbe, who's been involved in five of the rivalry's regular-season matches, believes there will be some of that intensity today.
"I think so, maybe not as much. But definitely a little bit," said the 22-year-old, who won an NCAA title while playing at Akron.
Both teams may be about 1,500 miles from their Pacific Northwest home bases today, but their cities are just 170 miles apart - just a short car ride from enemy territory.
Historically, their rivalry has some distance. They started playing each other in 1975 in the North American Soccer League. Even when the NASL went defunct, the teams managed to meet many times in various leagues over the years. Seattle has won 42 matches, Portland has been victorious 28 times and the two have settled for eight draws.
When Portland joined Major League Soccer in 2011, the rivalry regained steam and picked up national visibility. Sellout crowds and the tifo, a choreographed display using massive banners, became the norm.
"I grew up in Seattle so I watched the series back in the 70s and early 80s in the NASL days," said Chris Henderson, the Sounders' sporting director. "Our biggest rival was the Timbers. They were always the team you wanted to beat because they're so close and the fans were so passionate about both teams."
John Galas, a longtime Portlander and the Timbers' performance analyst, is also quite familiar with the rivalry.
"It's passionate, it's healthy, it's great for the league," Galas said. "The fans are extremely involved in it. Sometimes it boils over a little bit. … It creates an unbelievable atmosphere."
Long, who was born and raised in Seattle but proudly displays his allegiance to the Timbers, says there's another factor to the rivalry.
"It's kind of a big brother-little brother thing," Long said. "I think Seattle always feels like they're the big brother just in general. And when you have the rivalry with the teams, it's even more so."
Then consider today's match just another instance of sibling rivalry.
• What: MLS Desert Friendly
• Who: Portland Timbers vs. Seattle Sounders FC
• When: 10:30 a.m.
• Where: Kino Sports Complex North Field No. 5