The veteran holding midfielder is hanging up the cleats after an illustrious career that saw him suit up in two World Cups and lift a MLS Cup.
"After 16 amazing years in MLS, I have decided that now is the time to step away from the game as a player,” Mastroeni said in a news release.
A tough central midfielder who retires with his name in the referee's book more than anyone else's, Mastroeni joined the LA Galaxy during the 2013 season in a trade from Colorado but will be rememberd as a Rapids legend. He captained Colorado from late 2004 until this year's trade and is currently the team's all-time leader in starts, appearances and minutes. In addition to lifting MLS Cup with the club in 2010, he also made seven consecutive All-Star teams between 2002 and 2008.
"Pablo’s contributions to the club can’t be overstated, and we all want to thank and honor him for his service to the Rapids. Pablo was a true competitor on the field, and over his time with Colorado, we all saw what a powerful impact he had on his teammates and on the fans. He’s one of the true greats of American soccer and will always be a Colorado Rapids legend," Rapids technical director Paul Bravo said in the release.
Before joining the Rapids, Mastroeni played all four seasons of the Miami Fusion's existence before the club contracted, and is tied atop that club's leading appearance list as well with 100. He helped the club to the Supporters' Shield in 2001 and was named to the league's Best XI that year.
For his country, he'll best be remembered for his performances in the 2002 World Cup when he helped the Americans to a group stage victory against Portugal and a knockout round win against Mexico before starting the quarterfinal loss against Germany. He also started the first two group matches of the 2006 World Cup, but, true to his gritty style, received a controversial red card against Italy and missed the final match.
The 37-year-old Mastroeni had previously considered retirement, but last month told MLSSoccer he was mulling continuing his career because he felt good in physical shape. The holding midfielder said he was up against "probably the toughest two weeks I've spent here (in LA), trying to figure all these things out, but I think in the end it will work out the way it should.”
In the end, though, having his family back in Colorado and not being re-signed by the Galaxy made the choice easier for Mastroeni.
"I want to thank my wife Kelly for all of her understanding, and for being the driving force in everything I've been able to achieve in my career. Finally, a huge thanks to my kids, Luca and Giuliana, for making me realize that there is actually something bigger than soccer," he said.