By Michael Fabiano What effect will free agency have on fantasy values? The start of the NFL free agent period begins on Wednesday, March 16, so we’ll soon start to see changes to rosters, depth charts and, of course, fantasy football values. With that in mind, I’ll be covering the four major fantasy positions and listing the top available players, including their best fantasy fits. I started things off with quarterbacks, so let’s move on to what some would argue is the most important position in fantasy, the running backs. Unlike the signal-callers, there are several big-name players who will…