Serena Williams did not appreciate John McEnroe's comments about where she'd rank among men's tennis players.

On Sunday, during an interview on NPR, McEnroe said Williams would rank "like 700" in the world if she played on the men's circuit.

While McEnroe called Williams the greatest women's player ever, he said she couldn't match up physically with men.

On Monday, Williams issued a calm but forceful response.

McEnroe has not apologized for the comment.

On Tuesday, he appeared on "CBS This Morning" and said he didn't intend to cause a controversy with his remarks, then he retroactively ranked Williams the fifth-greatest player of all time.

McEnroe, 58, also estimated that he would be ranked 1,200th in the world if he were playing today.