The Nets are going to be without at least one presumptive starter for the beginning of training camp Tuesday — and it’s not Ben Simmons.

Cam Johnson sustained a mild left hamstring strain during an on-court workout last week, and will miss the start of camp.

Brooklyn provided no other information about his estimated return date.

“I’m good. I’m good,” Johnson said Monday. “I do expect to play at some point in the preseason; just not these next couple days, and we’ll see how it goes over this next week.”

With Simmons finally recovered from the back woes that limited him to just 42 games total in the past two seasons combined, the Nets had expected to be whole for coach Jacque Vaughn’s first training camp in charge. No such luck.

After the trade of Kevin Durant to Phoenix in February, the 27-year-old Johnson arrived with Mikal Bridges as the foundations of the rebuild.

Johnson averaged 16.6 points and 4.8 rebounds on .372 percent shooting from deep in 25 games for the Nets.

A restricted free agent this past offseason, he signed a four-year, $94.5 million extension.

Then he proceeded to compete for Team USA in the FIBA World Cup.

The 6-foot-8, 220-pounder is expected to provide much of the team’s outside shooting.

He’s the only player on Brooklyn’s roster who hit over .400 from deep last season — .404 overall, and .452 for the Suns.

With the departures of Joe Harris, Patty Mills, Yuta Watanabe and Seth Curry (along with Durant and Kyrie Irving), the Nets will need all the shooting they can get this season.

Brooklyn categorized Johnson’s injury as “mild.”

Presumably he should be available by the regular-season opener (Oct. 25 vs. Cleveland), although it remains to be seen if he’ll play in any of the Nets’ four preseason tilts.

Their first is Oct. 9 against the Lakers in Las Vegas.