In the premiere episode, when Dr. Will Halstead (Nick Gehlfuss) miraculously getting his job back is the main plot point, he can’t do so without some strings attached. One of those strings is Dr. Matt Cooper. Cooper is a newcomer who knew Will before joining the ED. Goodwin (S. Epatha Merkerson), has asked Will to spy on his co-worker to fulfill his conditions for rehire.
Will doesn’t want to, but Goodwin needs someone that Cooper trusts to get the intel on him. Goodwin seems to believe that Cooper might be selling poor-quality monitors for his patients so that he can make money off the VasicLabs monitors.
And because Will has something to prove and knew Cooper beforehand — in fact, Cooper dated Will’s cousin at one point — he has to be the guy to rat out Cooper if he is dealing dirty.