The first day of NBA training camp is supposed to be accompanied by brimming optimism, a time for players and coaches all taking those first steps toward what they hope is a championship.

Such was the case Tuesday — in a very tempered fashion.

The first preseason camps of the coronavirus era are formally open, with teams limited for now to individual sessions with one coach and one player at one basket, all of this starting to happen as the pandemic continues raging and more and more Americans are testing positive.

“I’m very concerned if we can pull this off,” Philadelphia coach Doc Rivers said.

He probably isn’t alone in that thinking.

Washington coach Scott Brooks said the Wizards already have seen one player test positive for coronavirus, and Orlando coach Steve Clifford said Magic center Mo Bamba — who tested positive several months ago — is still “a ways away” from being ready to play again. Later Tuesday, Golden State general manager Bob Myers said two Warriors have tested positive, meaning that club won’t start full-scale practice until at least Monday, a mere six days before its preseason opener.

There will likely be more positives. Probably many more.

Rivers, noting how the virus is becoming a major issue for college football and the NFL in terms of getting games played, said the effect on an NBA team losing a key player or two for even a short period could essentially wreck a season.