Per an official announcement from the Pelicans, Williamson didn't travel with the team to New York and is undergoing additional testing at Ochsner Sports Medicine.
Per ESPN's Adrian Wojnarowski (h/t ESPN's Andrew Lopez), New Orleans is being "cautious" and expects to know more in the next 24 hours, but this isn't necessarily a normal preseason "rest" situation.
In two preseason games, Williamson has been everything New Orleans could have hoped for. The former Duke star had a combined 48 points on 17-of-23 shooting with 15 rebounds against the San Antonio Spurs and Utah Jazz.
Williamson was selected by the Pelicans with the first overall pick in the 2019 NBA draft after a standout freshman season at Duke. He was named the Naismith College Player of the Year as college basketball's top player and earned consensus First Team All-American honors.
His campaign with the Blue Devils was limited to 33 appearances because he suffered a knee sprain after his shoe blew out during a rivalry clash with North Carolina. He played just one Las Vegas NBA Summer League game before being sidelined with a knee bruise.
If the latest ailment forces him to miss meaningful games, New Orleans will probably split his minutes between several frontcourt reserves. Nicolo Melli, Jahlil Okafor and Jaxson Hayes lead the group of players likely to see an uptick in playing time.
Ultimately, the Pelicans are always going to exercise extreme caution when it comes to Williamson. They showed that immediately by taking him out of the Summer League with a minor injury. Their lineup won't be nearly as dynamic in the interim, though.