And for what it's worth, Donovan is in good company: Several all-time greats in multiple disciplines share a similar experience. Here are some of the more notable returns in soccer and other sports:
Alexi Lalas (Soccer): The US Soccer Hall of Fame defender retired at the end of the 1999 season with Kansas City before returning to join the LA Galaxy in 2001 and winning MLS Cup and US Open Cup titles with the club before calling it a career on January 12, 2004.
Robbie Rogers (Soccer): In February 2013, Donovan's LA Galaxy teammate stepped away from professional soccer at age 25 after announcing he was gay. But just three months later he was back in MLS and playing for the Galaxy in LA, where he's been ever since.
Paul Scholes (Soccer): The former English international retired from the only club he ever knew, Manchester United, in May 2011 and the Red Devils even held a testimonial match for him. He reversed his decision seven months later in order to help the club before retiring for good in May 2013.
Pele (Soccer): The world great came out of retirement in 1975 to join the New York Cosmos in the old NASL, playing competitively until October 1977.
Jens Lehmann (Soccer): The former German international goalkeeper initially hung up his boots in June 2010, only to lace them back up for what was roughly a three-month emergency stint for Arsenal, who were experiencing a goalkeeper injury crisis.
Michael Jordan, Magic Johnson (Basketball): The most renowned comeback from retirement in all of sports arguably belongs to Michael Jordan. He left to pursue a baseball career in 1993 and then returned in 1995 to register a three-peat of titles. He retired again in 1999, only to return in 2001 to play for the team he owned, the Washington Wizards. His final competitive game came in April 2003.
After announcing he tested positive for HIV, Magic Johnson retired from the NBA in November 1991 and made a comeback at the age of 36, playing for the Los Angeles Lakers in the 1995-'96 season.
Mario Lemieux (Hockey): The NHL legend called it quits after the 1996-'97 season and was inducted into the NHL Hall of Fame just months later. However, he returned in December 2000 and went on to play several more seasons before calling it a career for good in January 2006 at the age of 40.
Roger Clemens (Baseball): The flame-throwing pitcher made a few retirement comebacks in his career -- in January 2004, June 2006, June 2007 and then in the Independent League in 2012 at the age of 50.
Brett Favre (NFL): Although other American football players have returned from retirement -- Deion Sanders, Reggie White, Randall Cunningham, Ricky Williams -- the former Super Bowl-winning quarterback is one of the more recent stories, calling it quits in March 2008 only to be back five months later with the NY Jets and eventually the Minnesota Vikings. He retired for good in January 2011.
Muhammad Ali, George Foreman & Floyd Mayweather (Boxing): Foreman had one of the most stunning returns in all of sports, coming back after 10 years to fight as a 38 year old. His old nemesis, Ali, retired in July 1979, but came back to lose the last two bouts of his career in 1980 and 1981. More recently, Mayweather came back from retirement in 2009 to box for several more years before hanging up the gloves in September 2015.
Michael Phelps (Swimming): The man with the most gold medals in Olympic history retired after the 2012 London Games, coming back two years later and paving the way for his record-breaking accomplishments at Rio 2016.