Horford is questionable for Monday's game against the Pelicans due to a left neck sprain, Marc D'Amico of the Celtics' official site reports.
Horford normally sits out at least one game during a back-to-back set, so it wouldn't be surprising to see him sidelined Monday versus New Orleans or Tuesday versus Indiana. Luke Kornet (hamstring) is doubtful and Kristaps Porzingis (ankle) is questionable, so Boston's frontcourt is in danger of being extremely shorthanded versus Zion Williamson and Jonas Valanciunas.