The Boston Celtics are looking to claw back into the series against the Miami Heat on Monday night but will once again be without a key defensive star for Game 4. According to Shams Charania, Marcus Smart has been ruled out for the clash against Miami, a major blow for the Celtics just hours before tip-off.

Charania indicates that the swelling in Smart's sprained right ankle had increased since Game 3, prompting the Celtics to sit him out for the clash on Monday night. With Smart on the sideline, Derrick White and Payton Pritchard are expected to see increased run.

Smart's absence will be a major loss for the Celtics, particularly on the defensive end. He's the reigning Defensive Player of the Year for a reason, so not having him available could result in Miami getting some better looks on the perimeter.

Smart has been banged up throughout the playoffs, having been hit with a slew of injuries against the Milwaukee Bucks. He will once again be forced to watch from the sideline on Monday as the Celtics look to avoid falling into a 3-1 hole against the Heat in the Eastern Conference Finals.

Miami is also dealing with its fair share of injuries, though the team confirmed that Jimmy Butler would be available despite leaving Game 3 early with a knee injury. While Butler has been cleared to suit up, Tyler Herro is sidelined with a groin injury, meaning the Heat will be without their leading bench scorer.

Ime Udoka and the Celtics will hope they can pull off the win at home with Smart on the sideline, but the job has just been made significantly more difficult.