Robert Smith, a 2x Pro Bowl runningback for the VIkings, had tiny calves. Even so, he averaged nearly 5 yard per carry (4.8) for his career, holds the record for average yards per touchdown at 27.2 yards per TD, and is the Vikings 2nd alltime leading rusher behind Adrian Peterson. Despite a series of early career injuries, he had four straight 1,000 yard seasons from 97-2000, and retired in his prime following the best season of his career when he ran for an NFL leading 1521 yards.
I have baby calves, and my senior year I was hand timed (in grass) at 4.56. Calf size means nothing.