Sentence:  "It has been a profitable trade period for the Blues. They also secured Dale Thomas as a restricted free agent and Sam Docherty from the Brisbane Lions, having lost Shaun Hampson in a trade with Richmond and Eddie Betts under <WSD>free agency</WSD>." 
Meaning of the word marked with <WSD> tags:  A system through which professional athletes are free to play for or sign a contract to play for any team.