D.C. United officials played down a knee appointment for Canadian international Dwayne De Rosario, saying it was just a precaution.
"Assessment on my knee today. Hope for positive result!:)," tweeted the star midfielder.
De Rosario, the MLS MVP in 2011, missed the last six weeks of the 2012 regular season after straining knee ligaments on international duty with Canada.
Asked about De Rosario's tweet, D.C. United coach Ben Olsen said the team just wanted to assess the knee before allowing the 34-year-old from Toronto to join the Canadian national team later this month for friendlies against Denmark and the U.S.
"It's not a big deal ... He's fine," Olsen told a media conference call.
De Rosario had seven goals and 12 assists in 26 games last season.
The call was to announce the signing of 20-year-old Brazilian striker Rafael as a "young Designated Player" on loan for one year. Rafael arrives from Brazil's Bahia.
Rafael, who represent Brazil at the 2011 Pan-American Games, is the youngest current Designated Player in MLS and the second-youngest in MLS history after Fabian Castillo (18 when he signed with FC Dallas).
Designated Players 20 years old or younger count as US$150,000 against the club's salary budget. A DP aged 21 to 23 counts as $200,000 against the club's salary budget.