Paul Millsap is not with the team due to tendinitis, according to the team's official Twitter handle,
Paul Millsap is not with the team in Miami due to right elbow tendinitis— Atlanta Hawks (@ATLHawks) November 19, 2013
The Hawks are likely to use the Gustavo Ayon lineup with Al Horford at power forward against the Miami Heat tonight with Millsap out.
This likely means more minutes (and more shots...heh heh) for Mike Scott against a Miami team that has been criticized for their lack of front court excellence.
There's no word yet from the team as to the extent of Millsap's injury, so it's likely that he is just day-to-day until further word comes down regarding his immediate or long-term future.
UPDATE: Per team source, Millsap is officially out tonight and day to day moving forward. This means the fan-awaited match-up with Josh Smith may have to wait if Millsap can't go this week.