The undercard fight is of such high stature that it will be having its own three-city press tour, with many expecting it to be one of the biggest PPV cards in recent history.
The WBA, WBC, and Ring Magazine junior welterweight titles will be on the line in a fight that Garcia has been waiting a long time for.
"This is the fight I wanted and the fight that I asked for. That is why I'm so happy this fight has been made and will be a part of this huge event," said Garcia.
"I'm more confident than ever in my abilities and I'm going to show it on September 14. Matthysse is a good fighter and has a big punch, but I'm a talented fighter with what it takes to be a champion and stay that way.
"This is an opportunity for the world to see what I can really do in the ring."
Argentine Matthysse believes that he is the best pound-for-pound fighter in the world and will be looking to prove that on September 14th.
"I'm glad I finally get a chance to fight Danny Garcia," said Matthysse.
"This is the fight that the entire boxing world, especially my country Argentina, and I wanted. I want to thank my promoters Golden Boy Promotions and Mario Arano for making this fight possible.
"On September 14, I will show the world that I am the best 140 pound fighter on the planet."