how to add a pseudo-element gradient effect

Hello how could i add to a pseudo-element gradient effect from left to right. i'm trying:

.divider p:after {
    content: "";
    position: absolute;
    top: 50%;
    left: 0;
    right: 25%;
    z-index: -1;
    border-top: 1px solid #666666;
}

HTML

<div class="divider">
 <p><span>Featured</span></p>

 </div><!-- end of divider -->

above code draws a sharp line,but i would like create something like this:

my whole code was:

.divider {
color: #666666;
}
.divider p span {
margin:0;padding: 0 10px;
background: #FFFFFF;
display: inline-block;
}
.divider p {
padding-left: 20px;
position: relative;
z-index: 2;   
}
.divider p:after {
content: "";
position: absolute;
top: 50%;
left: 0;
right: 25%;
z-index: -1;
border-top: 1px solid #666666;
}