Diaz jumped at the opportunity to play abroad after 5 1/2 seasons with Dallas.
"We love that [Diaz] is going and pursuing his future. We respect that," coach Oscar Pareja told FC Dallas Extra Time's Gina Miller prior to the club's Wednesday match against Atlanta United. "It is our responsibility to see that with this group we can keep pushing the team higher."
FC Dallas currently sit atop the Western Conference in large part due to Diaz. The Argentine playmaker made 109 appearances for Dallas, scoring 23 goals and recorded 88 assists. In 2016, Diaz helped FC Dallas to a Supporter's Shield and U.S. Open Cup double.
"It is never a right time to get Mauro Diaz out of the club," said technical director Fernando Clavijo. "He helped this club achieve stuff we have never achieved before.
"He asked the team, 'Can you do this for me?" Clavijo said. "The door is open. This is his home. If he ever wants to come back, hopefully we open the door and bring him back."