The Nets filled one of their three open roster spots Friday by preparing to sign free-agent big man Norvel Pelle.

The deal – which will be completed pending clearance of the NBA’s Health and Safety protocols – was first reported by ESPN and confirmed by The Post. Pelle will have to repeatedly test negative for COVID-19 before he can join the Nets.

Since trading away center Jarrett Allen last week in the four-team blockbuster deal for James Harden, DeAndre Jordan has been the starter by default with no true center to back him up or push him.

Brooklyn has been sorely lacking in size, shot-blocking and interior defense. GM Sean Marks bringing in the 6-foot-10, 231-pound Pelle should at least help in all three areas, especially rim protection.

Pelle averaged 3.0 rebounds, 2.4 points and 1.3 blocks in 9.7 minutes over 24 games last season with the 76ers. But at 27 years old, he’s taken a long, winding road to Brooklyn that would make Homer’s Odyssey seem like a day trip.

Born in St. John’s, Antigua and Barbuda, Pelle also lived in the U.S. Virgin Islands before settling in California.

The top-ranked center prospect nationally in his high school class, Pelle went pro and ended up playing in the NBA Developmental League, as well as Taiwan, Lebanon and Italy, before finally reaching the NBA last season with Philadelphia.

Now Pelle gets a chance to vie for a rotation spot on a contending Nets team in need of his services. Allen is gone, second-year big man Nic Claxton is out indefinitely and Kevin Durant is the only Net other than Jordan standing at 6-foot-10 or taller.

Jeff Green, at 6-foot-8, 235 pounds, is far more of a stretch 4 than a true center. Pelle could vie with 2020 second-round pick Reggie Perry for minutes. The 6-foot-8 Perry has played eight games, cracking double-digit minutes in the past four since Allen departed.

The Nets have until Jan. 30, two weeks from the date of the Harden trade being completed, to fill the two remaining open roster spots. They could elevate two-ways Perry and Chris Chiozza to full roster spots.

According to The Athletic, the Nets have been granted a Disabled Player Exception worth $5.7 million – half of Spencer Dinwiddie’s salary.

Brooklyn still has a clear need for a wing defender such as Andre Roberson, Corey Brewer or ex-Net Rondae Hollis-Jefferson.

The Nets could make a trade and they could hold a spot until the buyout market opens on April 9.