With the omicron variant spreading at shocking speed, the NBA and the players union have agreed to new rules aimed at helping teams field fuller rosters and helping the league avoid postponements. Teams are permitted to sign one replacement player for each player who tests positive for COVID-19, and teams are required to sign at least one replacement player if two test positive, at least two replacement players if three test positive and at least three if four or more test positive, per ESPN.

The new rules, which will be in effect until Jan. 19, stipulate that replacement players' salaries will not count toward the salary cap or luxury tax. When a team has multiple COVID cases on its roster and must sign a replacement, the player must be available by the beginning of its next game. For an NBA game to be played, both teams are required to have eight players available. The league has postponed nine games this season, and several teams have played severely shorthanded. 

Isaiah Thomas made his Dallas Mavericks debut on Wednesday, on a new 10-day contract after a short stint with the Los Angeles Lakers. Lance Stephenson, briefly Thomas' teammate with the Grand Rapids Gold, is now a member of the Atlanta Hawks, and seven-time All-Star Joe Johnson is once again a member of the Boston Celtics. The Celtics drafted Johnson in 2001, and he turned 40 in June, months before winning his second BIG3 MVP award. 

Another unlikely reunion: Mario Chalmers and the Miami Heat. The two-time champion is taking his talents back to South Beach after globetrotting from Italy to Greece to Puerto Rico. Chalmers, who last appeared in an NBA game in 2018 with the Memphis Grizzlies, is getting called up from -- you guessed it! -- Grand Rapids. If you're having trouble keeping track of who has gone where, here is a team-by-team list of players who are on 10-day contracts, along with the date they signed (or, in some cases, the day the signing was reported.

Atlanta Hawks

• Chris Clemons (Dec. 29)
• Cam Oliver (Dec. 29)
• Justin Tillman (Dec. 28)
• Chaundee Brown Jr. (Dec. 27)
• Cat Barber (Dec. 25)
• Malik Ellison (Dec. 25)
• Wes Iwundu (Dec. 23)
• Lance Stephenson (Dec. 22)
• Malcolm Hill (Dec. 22)

Boston Celtics

• Al-Farouq Aminu (Dec. 25)
• Norvel Pelle (Dec. 25)
• Joe Johnson (Dec. 22)

Brooklyn Nets

• Shaquille Harrison (Dec. 29; second 10-day)
• Langston Galloway (Dec. 26; second 10-day)
• Wenyen Gabriel (Dec. 21)

Chicago Bulls

• Jordan Bell (reported Dec. 29)
• Ersan Ilyasova (Dec. 23)
• Mac McClung (Dec. 23)

Cleveland Cavaliers

• Malik Newman (Dec. 29)
• Trevon Scott (Dec. 22)
• Justin Anderson (Dec. 21)
• Luke Kornet (Dec. 21)

Dallas Mavericks

• Isaiah Thomas (Dec. 29)
• Charlie Brown Jr. (Dec. 23)
• Carlik Jones (Dec. 23)
• Brandon Knight (Dec. 23)
• George King (Dec. 22)
• Marquese Chriss (Dec. 21)

Denver Nuggets

• Davon Reed (reported Dec. 30; third 10-day)