NEW YORK -- Saturday is known as "moving day" on the PGA Tour, and that works at this hopping, popping US Open too. Players are vying for a coveted spot in the second week and a berth in the fourth round. Here's what you need to know on Day 5:
Watch every match
At 11 a.m. ET, ESPN3 will carry full coverage of seven matches. Click to watch multicam.
At 11 a.m. ET, ESPN and WatchESPN begin coverage. Click to watch.
To view starting times of upcoming days at the US Open, click here.
Live scoring
Our real-time scoreboard, updated stats and social handles can be found on one spot, US Open CourtCast.
Brackets
Find out who's moving on (and who's not) with our US Open men's and women's brackets.
Saturday's key matches
No. 11 David Ferrer versus Juan Martin del Potro, third match on Louis Armstrong Stadium (Watch)
The unseeded del Potro hasn't dropped a set in two matches at the US Open and is playing some sizzling tennis this summer, highlighted by his run to the Rio Olympics final. These two have quite a history, encompassing nine matches. Del Potro won the last one, at Wimbledon in 2013. Ferrer is 34 years old and still a handful.
No. 1 Serena Williams versus Johanna Larsson, not before 1 p.m. ET on Arthur Ashe Stadium (Watch)
Worries about the sore right shoulder that forced Serena to withdraw from Cincinnati seem to have vanished. She isn't hitting the ball as cleanly as she would like, but she's been composed, which will help her going forward. Williams is 2-0 head-to-head against the Swedish player.
No. 2 Andy Murray versus Paolo Lorenzi, after Serena-Larson (Watch)
Murray has looked like the favorite so far, averaging better than 6-3 for each of his six sets. The two have played only once, and it was 10 years ago in Adelaide, Australia. Murray won in three sets.
No. 21 Ivo Karlovic versus James Donaldson, fourth match on Court 17 (Watch)
The 19-year-old American has defied gravity so far, and now he has a chance to reach the second week here. He'll have to get past Karlovic, who stroked a US Open-record 61 aces in his first-round match and 24 more in the second.
No. 6 Venus Williams versus No. 26 Laura Siegemund, 7 p.m. ET on Arthur Ashe Stadium (Watch)
This might be tougher than it looks. Venus, 36, was extended to three sets in her first-round match and tends to fatigue as the matches mount. Siegemund reached the quarterfinals of the Olympics, losing to eventual gold medalist Monic Puig.
No. 14 Nick Kyrgios versus Illya Marchenko, after Venus- Siegemund (Watch)
Kyrgios, the brash 21-year-old Aussie, has been making waves again this fortnight. You never know what he's going to do on court, but more often than not, he wins. At the US Open, he's won all six sets. Marchenko, the 28-year-old Ukrainian, is one set over the minimum.