Heavyweight knockout artist  Derrick Lewis scored another finish on Saturday in the UFC St. Louis main event.  Lewis knocked out Rodrigo Nascimento early in the third round after knocking him down with a right hand.   Lewis entered the bout coming off a decision loss to  Jailton Almeida in his previous fight back in November. He had lost four of his last five bouts and was in desperate need of a win to stay relevant in the division