D.C. United unveiled its new secondary jersey to season-ticket holders on Sunday, a jersey that introduces a host of new features, including an explicit nod to longtime supporters groups and a burst of red.

The secondary jersey also is a departure from the team’s history. The club has traditionally introduced new primary and secondary jerseys at the same time every two years, with the secondary jersey often mirroring the main kit, just in different colors. This time, the team waited three years to introduce its new secondary jersey, putting the two jerseys on different cycles moving forward.

The new design is also strikingly different from the primary black kit, putting the club in line with international teams (and some MLS outfits) that use the secondary jersey as chance to experiment with more than just the coloring.

So, what are the changes?

* In perhaps the coolest feature, the team inserted one of the classic cheers used by the Barra Brava, Screaming Eagles and others — “Vamos United Esta Noche Tenemos Que Ganar” — on the inside of the jersey’s necktape. Loosely translated as “Let’s Go United, Tonight We Must Win,” the slogan has been a staple for the singing throngs on RFK Stadium’s “Loud Side.” The slogan will also appear on scarves and other merchandise being released in conjunction with the new jerseys.

* Focus groups involving United season-ticket holders, supporters groups and youth players revealed two key takeaways: people wanted more red in the secondary jersey, and a return to the horizontal striping from the team’s early years.

That latter issue is complicated by the introduction of jersey sponsors; the early jerseys had three horizontal stripes, which is an Adidas trademark, and the club cannot put the name of a different sponsor over an Adidas mark. Plus, putting the three stripes beneath the jersey sponsor made them look like belly stripes, which wasn’t ideal.

To avoid that problem, the team and Adidas together came up with a more complex striping pattern, with large red stripes gradually decreasing in size. (As part of the process, designers looked at various international striped patterns, including those used by Chelsea, Stuttgart VfB, Hamburg and AC Milan.)

As for the red, it’s the dominant color on the upper half of the shirt, making this the reddest secondary jersey the club has ever used. (There have been all-red third kits in the past; the club no longer has a third jersey.)

“We call ourselves the black and red, but if you look at [last year’s secondary jersey], there’s so little of that red incorporated,” director of merchandising Nathan Fry said. “You’ve seen very little red historically.”

* The team crest on the secondary jersey is lenticular, giving it an illusion of depth. The original design called for an all-black lenticular crest, which looked almost Batman-like, and kind of severe. Coach Ben Olsen — an accomplished artist — grabbed a silver sharpie when he saw it and sketched out a more subtle version, with the same hologrammed feel.

“In general, I think we’re taking the direction that our primary kit is going to look very classic year after year,” Fry said, “And then we’re going to take more freedoms with the design elements on the secondary kit, like using a lenticular crest.”

* The logo on the back collar is also a departure from, well, tradition. The back of the primary jersey reads “Tradition” on the back collar, a word the club has used heavily throughout its 20 years. The secondary jersey will instead have the eagle logo from the team’s crest on that area.

The process of designing these jerseys is surprisingly complex; planning for this one began about 24 months ago, and involved repeated back-and-forths with the Adidas design staff. Fry predicted the end result will become the club’s best-ever selling jersey.

“I like it more every time I look at it,” he said. “The combination of the lenticular crest, the supporters-inspired necktape on the inside, and the addition of so much red, that all will make this more popular than anything we’ve done in the past.”

Because the jersey is new, it will probably be used more often than last year’s secondary jersey, including at the season-opening CONCACAF Champions League match Feb. 26 in Costa Rica. (United will still wear its more traditional black kit for the majority of matches.) The new striping pattern will be featured in hats and scarves and other merchandise, as will the increased prominence of the eagle logo. (See below.) And this will start a new pattern for the club: in even years the team will release a more traditional primary kit, and in odd years, a more daring secondary kit.

“This is the first time that we’ve made that conscious effort to take more freedoms with the secondary jersey and start to do some cool things with it,” Fry said. “That’s a trend you’ve seen in the past couple years, and I think we’ll continue to push the design of the secondary jersey more and more.”