ST. JOSEPH, Mo. — The presumptive favorite to win the starting right guard spot with the Kansas City Chiefs worked out with the third team on Monday. The guy who is challenging him for the spot slid over to center during another portion of the workout.Rishaw Johnson and Zach Fulton are just the start of the offensive line shuffle.After watching three linemen who started last season depart in free agency — all within hours of each other — the Chiefs are trying to cobble together some sort of protection for quarterback Alex Smith that can also manage to open up running lanes for Jamaal Charles during training camp.And with lingering questions about the health of left tackle Eric Fisher and an ankle injury to starting right tackle Donald Stephenson, that job hasn’t gotten a whole lot easier.“People are saying that we are really young and we’ve got something to prove,” said Fulton, a sixth-round pick who could end up starting the Chiefs’ season opener Sept. 7 against Tennessee. “In a sense that’s good.