2013: Nyassi was released by the New England Revolution on May 16 and signed with D.C. United on May 27.
2012: Made one regular-season appearance. Suffered a right hamstring injury on Feb. 10 in a preseason scrimmage against Boston College. Was placed on the Disabled List on March 7 and was finally healthy enough to come off on June 27. Dressed for the first time this season against Seattle (June 30) but did not play. Made his season debut – and only appearance on the year – at Montreal (July 18), coming on as a 79th-minute substitute and played on the field with his twin brother, Sanna, for just the second time in their careers. Missed four matches (Aug. 25 against Chivas USA through Sept. 5 against Columbus) with a right adductor strain. Dressed for the final three matches of the year. Made six appearances, including five starts, in the MLS Reserve League where he scored two goals and added one assist. Started at left midfield at Columbus (June 10) and played 33 minutes, his first action since going on the Disabled List in March. Scored the game-winning goal in a substitute appearance at central midfield against Columbus (June 17). Recorded an assist on Mike Roach’s goal at Toronto (June 23), then scored his second goal of the season against New York (July 8).
2011: Made 21 appearances, including eight starts, scoring one goal. Missed much of the final two-and-a-half months of the season after suffering a right MCL sprain (Aug. 13 – Sept. 16) and a subsequent hamstring strain (Sept. 25-end of season) that he sustained when he returned to training following the knee injury. Scored his lone goal of the season at Seattle (June 26), his first goal since Oct. 2, 2010 – also against Seattle ... scored one goal ... appeared in the season opener at LA Galaxy (March 20), replacing Zack Schilawski at forward in the 74th minute. Started in the friendly against Manchester United (July 13). Entered as a 68th-minute substitute at Colorado (July 23), marking the first time that Sainey had faced his identical twin brother, Sanna, on the field at the same time in their careers. Appeared in both of the Revs’ U.S. Open Cup qualifying matches. Started the D.C. game (April 26) on the right wing and finishing stoppage time at left back. Played 60 minutes at Kansas City (May 25) on the left wing. Made four appearances in the MLS Reserve League, including two starts. Started and played the full 90 minutes against Columbus (Oct. 16), his first game action since Aug. 6.
2010: Made 28 regular-season appearances – including 27 starts – while recording new career-highs with three goals and two assists. His 28 appearances tied Pat Phelan for the most on the season, and his 2,297 minutes played led the team and marked a new career high. Scored his first goal of the season in the home opener against Toronto (April 10), and also earned an assist on Zack Schilawski’s first goal of the game. Tallied the second goal of a 2-0 win over the LA Galaxy (July 10) off a Shalrie Joseph rebound that was deflected by the goalie and hit the post. Assisted Iljia Stolica’s game-winning goal against Houston (Aug. 14). Made his first substitute appearance since Sept. 30, 2009 (span of 25 matches), when he came on at halftime at Chivas USA (Sept. 10) following his return from Gambia for its Africa Cup of Nations qualifier against Namibia. Recorded his career-high third goal of the season against Real Salt Lake (Oct. 2). Made three appearances in SuperLiga, including two starts. Came on as a second-half substitute in the 1-0 win over Pumas UNAM (July 14), and then started against Chicago (July 17) and Puebla (Aug. 4). Sat out the Monarcas Morelia game (July 20) as a precaution as he was carrying a yellow card. Missed the final against Morelia (Sept. 1) after being called up to the Gambia National Team for its Africa Cup of Nations qualifier against Namibia (Sept. 4). Also missed the Sept. 4 match against Seattle and the Oct. 10 match at Houston while with the Gambia National Team. Before missing the Sept. 4 match, Nyassi was the only Revs player to appear in every MLS match to that point in the season.
2009: Appeared in 28 matches - including 22 starts – in the MLS regular season, recording two goals and one assist. Overall, made 35 appearances, including action in the U.S. Open Cup, SuperLiga and MLS Cup Playoffs. Earned MLS goal of the week honors (Week 3) for his game-tying strike in the come-from-behind win over FC Dallas (April 4) in the home opener. Missed playing against his identical twin brother, Sanna, by just two minutes in the 1-0 win over Seattle (Aug. 20): Sainey started the match but was replaced in the 67th minute, while Sanna entered the match in the 69th minute. Earned his second career assist on Kheli Dube’s 81st-minute goal in the 4-2 loss to Kansas City (Sept. 5) after coming on as a substitute. Scored his fourth career goal in the 1-1 draw with New York (Sept. 18). Suffered a mild concussion in the 2-1 win over Seattle (Sept. 26), but recovered to make a substitute appearance in the next match against Dallas (Sept. 30) and start against Colorado (Oct. 3). Appeared as a substitute in the Revs’ lone match in the U.S. Open Cup – against the Harrisburg City Islanders (June 30). Started all four matches on the right wing in SuperLiga, but did not record a goal or an assist. Started both Eastern Conference Semifinal Series matches against Chicago in the MLS Cup Playoffs (Nov. 1 and Nov. 7).
2008: Appeared in 25 regular-season games, making 19 starts on the right wing. Scored two goals and added one assist in MLS action. Overall, made 33 appearances with 27 starts. Earned his first career start in the season opener against Houston (March 29), and scored his first MLS goal in stoppage time on a spectacular individual run from midfield, earning him Sierra Mist Goal of the Week honors for Week 1. Notched the game-winning goal at Kansas City (April 9). Missed the match at FC Dallas (April 24) with a right adductor strain, then suffered a left quad strain while training and missed two more games: against Chicago (May 3) and at Chivas USA (May 11). Finally returned to the field as a second-half substitute against San Jose (May 17). Started as a withdrawn forward against D.C. (May 29) while countryman Kenny Mansally was with Gambia's national team, but later returned to his normal right wing position. Picked up an assist on Adam Cristman's goal against Dallas (June 6). Missed the game at Toronto (Aug. 23) while serving his yellow-card accumulation suspension and the match at Kansas City (Oct. 11) while representing Gambia. Started all five SuperLiga matches, and helped create Kheli Dube's game-winning goal against Santos Laguna (July 13), but was not credited with an assist. Started the away leg of the CONCACAF Champions League series against Joe Public FC in Trinidad (Aug. 26).
2007: The late-season signee made his MLS debut at D.C. on Sept. 9, playing the final eight minutes on the right wing. Made just the one MLS appearance with the first team, but made four appearances with the reserve side after his signing. Scored two goals, including his first goal - against the New York reserves - on Sept. 22. Scored again in his next reserve game, this time at Chicago on Oct. 7. Made his first-ever Revs appearance as a substitute winger in the Revs' victory over the Carolina RailHawks in the U.S. Open Cup semifinals on Sept. 4 when he helped create Pat Noonan's game-winning goal in extra time that sent the Revs on to the finals.
Has two caps with Gambia’s National Team as of Jan 30, 2010. In 2008, earned his first call-up to Gambia's senior national team for the nation's World Cup Qualifier against Senegal (Oct. 11), but did not play . He was called up for the country’s scheduled friendly against Gabon on Feb. 11, 2009, but the match was cancelled because of inclement weather. Nyassi was called in for the country’s three friendlies in January 2010 and has earned 16 caps for Gambia's Under-20 National Team, scoring one goal. His most recent U20 action came on Oct. 12 against Ghana in an African Youth Championships qualifier. The midfielder started all four of Gambia's games at the 2007 FIFA Under-20 World Cup in Canada. He also played a key role in Gambia's advancement to the semifinals of the African Youth Championships that year. Nyassi is a former member of Gambia's Under-17 National Team.
Signed with D.C. United on May 27, 2013.