Celtics sign seven-time All-Star Joe Johnson to 10-day contract

Johnson, 40, has spent the last three seasons as an unsigned free agent, last playing for a Houston Rockets team that made it all the way to the Western Conference Finals in 2018. He averaged six points in 23 regular-season games for the Rockets, although he only started in one of those games.

Johnson is the one of several players the Celtics signed this week to fill out their COVID-depleted roster. Boston signed veteran small forward C.J. Miles to a 10-day contract earlier this week. 

The contracts are among a string of hardship signings NBA teams have completed in order to put full rosters on the court as the recent COVID wave sidelines multiple players. Familiar big-name players such as Isaiah Thomas (Los Angeles Lakers) and Lance Stephenson (Atlanta Hawks) have also returned to the court on 10-day contracts so teams don't have to postpone games due to not having enough players suited up.

The NBA has also flexed the rules regarding call-ups from G league teams to fill out rosters and avoid game postponements. 

The list of players in COVID protocol is still evolving and changing.