Celtics' Marcus Smart, Al Horford to miss Game 1 of Eastern Conference Finals

The Boston Celtics will be short-handed when they begin the Eastern Conference Finals against the Miami Heat on Tuesday. According to Shams Charania of The Athletic, both Marcus Smart and Al Horford have been ruled out for Game 1.

Smart, 28, was previously listed as questionable due to a foot sprain suffered in a Game 7 win against the Milwaukee Bucks. Last month, Smart became the first guard in more than two decades to win NBA Defensive Player of the Year honors.

Horford, 35, was declared out for Tuesday after landing in the NBA's health and safety protocols, presumably meaning he tested positive for COVID-19. Horford averaged 10.2 points and 7.7 rebounds during the regular season, but erupted for 30 points during a Game 4 win over the Bucks.

Although Boston will be without two of its top defenders for Game 1 against the Heat, the team expects to get "significant minutes" out of center Robert Williams, according to ESPN's Adrian Wojnarowski. Williams missed the first two games of a first series against the Brooklyn Nets and the last four games against the Bucks due to a knee injury. 

The Celtics allowed the fewest points in the NBA during the regular season, while the Heat finished fourth.