Prior to the 2011 Major League Soccer season, Daniel trialed with the Philadelphia Union. Following the successful trial, Daniel signed with the Union on 18 March 2011. In Week 7 of the season, Daniel was named to the MLS Team of the Week for his performance against the San Jose Earthquakes. His first goal for Philadelphia was scored on 11 June 2011 in an MLS game against Real Salt Lake.
After temporarily leaving Philadelphia to play for the Trinidad and Tobago national football team in September 2011, Daniel was forced to remain in Trinidad and Tobago due to an expired visa until February 2012. This incident spawned the "Free Keon" meme used amongst Philadelphia Union fans at live matches and online social networking groups.