Carlos Beltran had surgery on his troublesome right knee Wednesday and the center fielder will miss the start of the season. His decision to have the operation also sparked a dispute about whether he had received permission from the team, and perhaps whether the surgery was needed. A person with knowledge of the situation said Beltran did not obtain advance written consent from the club to have the surgery, which was performed by his personal physician, Dr. Richard Steadman, in Colorado. The person spoke to The Associated Press on condition of anonymity because the Mets didn't discuss the matter publicly. Beltran's agent, Scott Boras, said the guarantee language in the player's contract requires advance written permission only for elective operations. "This was necessary surgery, necessary surgery to work," Boras told The Associated Press. The Mets might claim that the operation was elective.