Depends on what state you are in. There are some states that have a 3 day or 7 day waiting period in which the person is not entitled to compensation until after the waiting period. What does your policy say? If you don't have a policy and your state law says there is a 3 day waiting period then you do not have to pay the employee until the 4th day they are out (although some states have laws that say if the person is going to be out for a long period of time that they will go back to the first day the person is out and pay them whatever the percent of their salary is that they are entitled to base on that state law.) States have put this waiting period in to try to minimize the number of people being out for just a couple of days and "milking" the system.
What state are you in? Maybe someone here is familiar with the WC laws in that state.