Serena Williams nearly crashed out of the rain-hit US Open, but managed to stave off a challenge from a teenager to stay in the tournament.

Eighth seed Serena Williams, seeking her 24th career Grand Slam title to match Margaret Court’s all-time record, got a scare before ousting 17-year-old US wildcard Caty McNally 5-7, 6-3, 6-1.

McNally, who hadn’t been born when Williams won her first Slam at the 1999 US Open, threatened a struggling Williams from the start before the six-time US Open champion won nine of the last 11 games to escape under the roof at Arthur Ashe Stadium.

“I survived tonight. I’m not too pleased with the way I played at all,” Williams said.

“Serena, you made way too many errors today. What were you thinking?’ But I’m alive. I’m happy. I’ll do better next time. I promise.”

What the year’s final Grand Slam event lacked in quantity, with 22 singles matches postponed by showers, it overcame with quality in amazing matches that challenged three of the greatest stars in tennis history.

One point from surrendering a break into a tie-breaker, McNally won six of the final seven points, the last on a service winner, to capture the first set. Both players made 15 unforced errors. (AFP)