One of the regulars at Fortune‘s annual Most Powerful Women Summit is Billie Jean King. Going strong at 66, she and Ilana Kloss, who heads World TeamTennis (Billie Jean’s baby), put on a tennis clinic at the Summit each year. Let’s just say, it’s amusing to see type-A super-competitors of the business world sweating and struggling to ace it on the court.

I thought of King this weekend when I read “Confessions of a Sportswriter” in this week’s issue of Sports Illustrated. The piece was written by a guy who is, like her, an icon: Frank Deford, who started writing for SI in 1962 and has won about every award there is to win in his field. As soon as I finished Deford’s piece, I emailed King (who has won 39 Gland Slam tennis titles) to ask about her latest little challenge: She had both of her knees replaced. So, how’s she doin’?

She replied: “Thanks for the good wishes. It hasn’t been easy, a lot of pain…had surgery Feb 10th, going to rehab 3 times a week and doing stuff at home. Lots of ice for swelling (and medication!) Can’t wait to get back on a tennis court and hit a few balls.

That spirit you detect in her email is, come to think of it, what made King great–great through the fiercest pressure, beyond her obvious athleticism. (“Pressure is a privilege,” she likes to say.) In the current SI story, Deford cites King as evidence of how TV, in the 1970s, turned athletes into personalities, “not just distant performers on the field…athletes became more human and thus potentially more heroic.” He writes:

So I was very fortunate to be covering tennis when Billie Jean King took the bull by the horns. Billie Jean more than anyone else raised my consciousness. Here she was, virtually running a sport, getting up at 6 a.m. after a night match to appear on Sunrise in Cincinnati or some other TV show, serving as a symbol for a whole movement, taking a lot of crap from people who didn’t appreciate her–and winning championships. I knew she would beat Bobby Riggs in their Battle of the Sexes in ’73. Only two or three times in my life have I been dead sure of an outcome in sport, and that time is at the top of the list. Apart from the fact that Billie Jean was simply a better player than Bobby was then, and immune to pressure, she was really a lot like him. They both knew how to work a crowd, only Bobby was in it for the con, Billie Jean for a cause.

Keep on recovering, BJK. Keep on!