Game Five is on Monday night in Philadelphia.
"We'll be ready, I can guarantee you that," 76ers coach Doc Rivers said.
Embiid started despite a right thumb injury that required him to wear a brace.
"It's painful," Embiid said. "In basketball you need to use your hand a lot."
No team has ever come back from a 3-0 deficit to win an NBA playoff series. Fans briefly chanted "Raps in seven" after both coaches emptied their benches in the final minutes.
Embiid said he injured his thumb in the first half of Wednesday's Game Three, and had it taped at halftime. He finished that game with a decisive 3-pointer in overtime, but wore a brace afterward, and at Friday's practice.
Although Rivers said the Sixers don't believe the injury can get worse, Embiid was seen shaking his hand in pain several times on Saturday, occasionally doubling over as he squeezed the area.
"It's going to be something he's going to have to deal with throughout the playoffs from this point on," Rivers said. "It's not going to go away. He'll get better and better at figuring out how to use it."
Embiid shot 3 for 10 in the first half. He finished 7 for 16 and scored 21 points in 39 minutes.
Embiid said he expects to undergo an MRI in Philadelphia Monday but will likely keep playing even if doctors recommend surgery.
"I want to play," he said. "I would imagine that I keep playing and probably do something after the season."
Rivers said the Sixers, who made 16 turnovers and were outrebounded 46-41, didn't deserve to win Saturday.
"We just made so many mistakes," he said. "You can't win an NBA regular season game with the mistakes we made, let alone a playoff game."
Thaddeus Young scored 13 points, OG Anunoby had 10, and newly crowned NBA Rookie of the Year Scottie Barnes had six points and 11 rebounds off the bench as Toronto overcame an injury to All-Star guard Fred VanVleet to stave off elimination.
After being called for a foul with 4:57 to go in the second quarter, VanVleet ripped his jersey apart in frustration and walked off the court to the locker room because of a strained left hip.
"He's been banged around pretty good this year and he continues to lace it up and go out there and play big minutes every night," coach Nick Nurse said. "There's not every guy in this league that does that."
Joel Embiid goes 7 for 16 in 39 minutes of action.
Nurse said VanVleet was going for an MRI after the game. VanVleet shot 2 for 6 and scored five points in 15 minutes.
Tobias Harris had 15 points and 11 rebounds and James Harden scored 22 points for the 76ers. Harden shot 5 for 17, going 2 for 10 from 3-point range.
After being held scoreless in the second half of Toronto's Game Three loss, Siakam shot 10 for 19 and went 13 for 15 at the free throw line.
"It's about moving forward, and that's what he did," Young said of Siakam.
Trent had scored 20 or more in consecutive games after being slowed by an illness in Games 1 and 2.
"I wish I felt like this the first two games," Trent said. "My body is feeling good."
Philadelphia called timeout with 9:10 left in the fourth quarter after Young's steal on Embiid's wayward pass led to a driving basket for Achiuwa, giving Toronto an 88-81 lead.
Harden's layup with 8:20 to go made it 90-85, but Toronto scored the next six points, all at the free throw line. Embiid stopped the run by making a pair at the line, but Anunoby's 3-pointer with 3:44 to go in the fourth gave the Raptors a 99-87 edge.
Ahead of tipoff, the NBA announced that Toronto's Barnes had won the Rookie of the Year award, edging out Cleveland's Evan Mobley. The difference of 15 points was the smallest margin in the rookie category under the current voting format that began with the 2002-03 season.
Barnes left Game 1 of the series after spraining his left ankle and hadn't played since, but came off the bench midway through the first quarter Saturday.
Barnes needed treatment after falling down on defense early in the second, but remained in the game.
Embiid missed all five shots he took in the first quarter, including one from 3-point range.His only point in the opening period came when made one of two free throws.
Toronto led 54-49 at the half. Embiid shot 4 for 5 and scored eight points in the third but the Raptors took an 80-77 lead to the fourth.
FOUL LINE STORY
For the first time in the series, the Raptors shot more free throws than the 76ers. Toronto went 28 for 35 at the line, while Philadelphia was 21 for 25.
76ers: Harden had nine assists. … Tyrese Maxey shot 4 for 12 and finished with 11 points. … Embiid was called for a technical foul in the fourth quarter.
Raptors: Siakam had eight rebounds. … Young had five rebounds and five assists. … Canadian singer Avril Larvigne attended the game.
The 76ers host Game 5 on Monday night.
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