The Philadelphia 76ers will be severely short-handed for their game against the visiting Boston Celtics on Thursday.All-Star center Joel Embiid will miss the game with a dislocated left ring finger, suffered during Monday’s 120-113 win over the Oklahoma City Thunder. Embiid left in the first quarter but managed to return after having two fingers taped together.Embiid saw a specialist and could be out longer than one game. Despite the injury, Embiid had 18 points, nine rebounds and a season-best eight assists against the Thunder.The Sixers are 3-4 without Embiid this season.”I’m trying to beat the Boston Celtics and prepare the team to beat the Boston Celtics,” Sixers head coach Brett Brown told reporters. “But to go think that I’m not thinking longer, whatever the news that comes out, would be disingenuous.”Philadelphia, which will attempt to improve to 18-2 at home, will receive a lift, however, with the return of Matisse Thybulle. The Sixers’ rookie sat out for the last seven games with a right knee sprain and bone bruise.The Sixers will look to build on Monday’s seven-point win, which followed after a season-high four consecutive losses. Josh Richardson led the way with 23 points while Tobias Harris also added 18.Richardson has pointed repeatedly to being aggressive individually and as a group.”I think it kind of gives us a different look when I’m aggressive like that,” Richardson said. “I have to take it upon myself to do it a little more often, like every day. I’m a very unselfish guy, so sometimes I get caught trying to get my teammates going the whole game and not looking for my own offense.”The Celtics will arrive in Philadelphia following a frustrating 129-114 loss to the visiting San Antonio Spurs on Wednesday.Five Celtics reached double figures — Gordon Hayward with 18, Jaylen Brown (16), Daniel Theis (15), Jayson Tatum (14) and Marcus Smart (12) — but they were soundly defeated.Kemba Walker, who had missed the previous three games with flu-like symptoms, played 18 minutes while on a minutes restriction. Uncharacteristically, Walker was whistled for two technical fouls and ejected in the third quarter for arguing a non-foul call on a pick by Aldridge. Head coach Brad Stevens was also called for a technical foul.Walker finished with six points and four assists as the Celtics dropped their second straight for the third time this season. It was his first ejection in a sparkling nine-year career.”I thought I was being nice,” said Walker, who has earned the NBA sportsmanship award twice. “I thought the ref missed the call. The rest is history. … I mean, it’s the first time I’ve been ejected in my whole life. I am a two-time sportsmanship award winner as well. So maybe I should get a little leeway.”Now, the Celtics will turn their attention to another difficult matchup, even if the Sixers are missing Embiid. In their last two games, both losses, the Celtics have started slow and couldn’t recover.”We didn’t play hard enough. San Antonio played hard and we didn’t,” Stevens said. “San Antonio played great, we hoped a few shots went in so we could stay afloat. But we’re not playing hard enough the last two games, bottom line. The other teams deserve credit for beating us.”The 76ers have won both head-to-head meetings with the Celtics this season, beating Boston at home on opening night and on the road on Dec. 12.