NEW YORK – For the second-straight round, Venus Williams was up against someone she had never faced in her career. On Saturday, that distinction belonged to Germany's Laura Siegemund, who is ranked No. 27 in the world – her highest ranking to date. On this day, though, she was no match for the American veteran.

Venus needed just 78 minutes to get past Siegemund, defeating her 6-1, 6-2, to advance to the fourth round at the US Open.

En route to the convincing victory, Venus won 73 percent of her first serves while winning 74 percent of her net points.

While she did commit 26 unforced errors on the day, Siegemund played a decent game. Her only issue – and it was a big one – was that Venus was in vintage form.

Venus is now three rounds down in Flushing Meadows and she is looking progressively better with each passing game. Venus's schedule, though, only gets tougher as she will be up against No. 11 seed Karolina Pliskova in the fourth round.

The 24-year-old Czech is celebrating her longest run in a Grand Slam but lost her only meeting with Venus, falling in the final at Zhuhai (China) last November.

One of the biggest stories on the men's side came from 19-year-old Jared Donaldson, who has been turning quite a few heads despite his age.

After ousting No. 12 David Goffin and veteran Viktor Troicki, many were led to believe that the young American just might make leave the US Open in a New York state of mind. However, Donaldson's third-round opponent had something to say about that.

On Saturday, Donaldson faced a man 18 years his senior in Ivo Karlovic.

Ranked No. 23 in the world, the lanky Croatian had, unlike his opponent, entered the third round quietly, defeating American Donald Young in the second round after needing a five-set marathon to get past Taiwan's Yen-Hsun Lu in the opening round earlier this week.

On Saturday, Karlovic was victorious again, defeating Donaldson 6-4, 7-6(3), 6-3, to advance to the fourth round.

En route to his victory, Karlovic fired 14 aces and 54 winners while taking 79 percent of his first serves. Even with 24 unforced errors, Karlovic was not to be beaten on this day as he ends the American teen's impressive run in New York.

Waiting for Karlovic in the fourth round will be No. 7 seed Kei Nishikori who made the US Open Final in 2014. To say that Nishikori will be Karlovic's biggest test this week is most likely the understatement of the tournament.

In three previous meetings between the two, however, Karlovic has won twice. Nishikori, though, won the most recent meeting, a victory in the Memphis Open Final in July 2014.