For the 30th time since they became professional tennis players, Venus Williams and her younger sister Serena Williams will face one another this week in a clash of two of the best to ever play the game.

For years, the sisters’ matches have been one of the most tantalizing fixtures in sports. Fans became accustomed to seeing the sisters compete against each other only at the very end of tournaments, when all the other would-be champions had packed up and gone home.

But here in the latter stages of their careers, age and family life have created new conditions. This year, they will face off in just the third round of the United States Open on Friday.

“I wouldn’t say it’s exciting,” Serena Williams said on Wednesday, “but it’s definitely going to be a really tough match for me. Once again, it’s early in the tournament. You know, it is what it is.”