If or when Bolivian forward Jaime Moreno steps on the field for D.C. United this year, he will be the only player in league history to have played in all 15 MLS seasons.
Chivas USA goalkeeper Zach Thornton and forward Ante Razov also have been around since the beginning, but each of them has missed a season along the way.
For the 36-year-old Marsch, meanwhile, "14 excellent years" were enough.
"It wasn't final until maybe around the first of the year, but I'd say that at the end of last season I was at about 95%," he said of his decision to call it a day.
"When you take into account my age, the concussion issue, how my body was kind of letting me know . . . that being a professional soccer player was physically agonizing at times, that, combined with the opportunities that I had coming available to me . . . made it pretty clear to me that it was the right time."
Tributes from teammates came swiftly Friday, the best of them from veteran Chivas USA and former Mexico national team defender Claudio Suarez.
"He's one of those players that you never want to see leave the game, that you always hope will keep playing," Suarez said.
Marsch ends his MLS career having played in 321 regular-season and 37 playoff games and having won three league championships and four U.S. Open Cups.
"As much as people will talk about my winning a lot, I think the thing that I regret the most is not winning more because I feel like I was on a lot of good teams and maybe if we had been a little better in one game or another maybe the numbers are even higher in terms of championships," Marsch said.
Even though he was a defensive midfielder, Marsch scored 34 goals and had 43 assists, but his playing career was defined more by attitude and approach than by statistics.
Shawn Hunter, Chivas USA's president, said Marsch "has helped shape our franchise both on and off the field. He always brought incredible passion, dedication and energy to everything he did throughout his career."
The U.S. will now be the beneficiary of that seemingly inexhaustible drive, with Marsch joining Zach Abdel, Mike Sorber and Pierre Barrieu as assistants to U.S. Coach Bob Bradley.
Bradley and Marsch have known each other for 18 years, ever since Marsch was a freshman at Princeton and Bradley was the Tigers' soccer coach. Their paths crossed again at D.C. United, with the Chicago Fire and with Chivas USA.
"He [Bradley] feels I have certain qualities and can help with the group," Marsch said. "I've already been studying a lot of videotape and going through some different things with the team. There'll be a little of everything, but in the end I think my most important role will just be working with the guys and the staff and continuing to create a good environment every day."
Marsch, who was on the field helping out when the U.S. team held its January camp at the Home Depot Center, will be there officially when the squad regroups in Carson on Wednesday ahead of a Feb. 24 match against El Salvador in Tampa, Fla.
Originally from Racine, Wis., Marsch and his wife and three children have lived in Manhattan Beach since he joined Chivas USA in 2006. His new job means the family can remain in Southern California.
It also means Marsch will be going to South Africa for the World Cup in June.
"Everyone I talk to is quick to point out what a great opportunity it is, and everyone's right, there's no question about that," he said. "But after being around here for a while you also realize that this is a huge responsibility.
"This team means a lot to soccer in this country and certainly what happens this summer" means a lot. "I'm just trying to do all the right things, [and] work hard."