Boston Celtics' Gordon Hayward, center looks to pass as Philadelphia 76ers' Matisse Thybulle (22) and Tobias Harris (12) defend during the first half of an NBA basketball first round playoff game Monday, Aug. 17, 2020, in Lake Buena Vista, Fla. (AP Photo/Ashley Landis, Pool)
Boston Celtics' Gordon Hayward, center looks to pass as Philadelphia 76ers' Matisse Thybulle (22) and Tobias Harris (12) defend during the first half of an NBA basketball first round playoff game Monday, Aug. 17, 2020, in Lake Buena Vista, Fla. (AP Photo/Ashley Landis, Pool) Credit: Ashley Landis

BOSTON — The Celtics say forward Gordon Hayward will be sidelined for around four weeks after suffering a severe right ankle sprain in Boston’s Game 1 win over Philadelphia in their first-round playoff series.

The injury occurred in the fourth quarter of the Celtics’ 109-101 victory Monday night when he went up for a rebound and rolled his ankle as he landed on teammate Daniel Theis’ foot. He limped to the locker room and didn’t return.

Hayward played 34 minutes and scored 12 points on 5-for-13 shooting with four rebounds before the injury, which the team described as a Grade 3 sprain, the most severe type.

The timeline for recovery means Hayward will miss the rest of the first round at a minimum and possibly some of the second if the Celtics advance. He already planned to leave the bubble for a time if the team was still playing in September. His wife is pregnant and is scheduled to deliver sometime next month.

With Hayward out, it could mean a shift to a three-guard lineup and more minutes for Marcus Smart, who has been filling the role of Boston’s sixth man. Smart played 32 minutes in Game 1. He started 40 games during the shortened regular season.

The Celtics went 14-6 without Hayward this season.

Inside Game 2

Philadelphia 76ers (43-30, sixth in the Eastern Conference during the regular season) vs. Boston Celtics (48-24, third in the Eastern Conference during the regular season)

WHERE/WHEN: Lake Buena Vista, Florida; Wednesday, 6:30 p.m. (visit gazettenet.com for coverage.)

LINE: Celtics -6; over/under is 217

EASTERN CONFERENCE FIRST ROUND: Boston leads series 1-0

BOTTOM LINE: The Boston Celtics play the Philadelphia 76ers in the Eastern Conference first round with a 1-0 lead in the series. The Celtics won the last matchup 109-101. Jayson Tatum scored 32 points to lead Boston to the victory and Joel Embiid scored 26 points in defeat for Philadelphia.

The Celtics are 9-6 in division play. Boston is ninth in the Eastern Conference with 47.8 points per game in the paint led by Jaylen Brown averaging 9.

The 76ers are 28-18 in Eastern Conference play. Philadelphia is sixth in the league allowing only 108.4 points while holding opponents to 46.3% shooting.

TOP PERFORMERS: Tatum is shooting 45% and averaging 23.4 points. Brown is averaging 16.6 points and 5.2 rebounds over the last 10 games for Boston.

Embiid is averaging 23 points, 11.6 rebounds and 3.0 assists for the 76ers. Tobias Harris is averaging 18.2 points and seven rebounds while shooting 41.7% over the last 10 games for Philadelphia.

LAST 10 GAMES: Celtics: 7-3, averaging 117.4 points, 46.4 rebounds, 23.7 assists, 8.7 steals and 5.6 blocks per game while shooting 46.6% from the field. Their opponents have averaged 110.4 points on 44.5% shooting.

76ers: 5-5, averaging 118.6 points, 46.2 rebounds, 25.3 assists, 6.7 steals and 4.7 blocks per game while shooting 48.7% from the field. Their opponents have averaged 114.6 points on 46.4% shooting.

INJURIES: Celtics: Gordon Hayward: (right ankle) out.

76ers: Glenn Robinson III: out (oblique), Ben Simmons: out for season (knee).