Philadelphia 76ers head coach Doc Rivers is unsure when Joel Embiid will return from injury after a knee sprain sidelined the MVP favourite for Game 4 against the Brooklyn Nets.

It was announced on Friday that Embiid had suffered the injury in Thursday's Game 3 win over the Nets – the 76ers' third straight victory in the series.

Embiid has sustained injuries during several previous postseason campaigns, including sitting out two games as the 76ers were beaten by the Miami Heat in last year's Eastern Conference semifinals.

An ESPN report suggested Embiid could return to the court as early as next week, but Rivers was unwilling to put a timeframe on the center's recovery on Saturday.

"This is another obstacle in the story that we're going to write this year, and we're going to be okay. It may take a minute, but this is just part of it," Rivers said.

"He's human, and goodness, this happens again. Let's win, let's get him back on the floor and let's keep on our own journey."

Asked whether Embiid could return during this series if Brooklyn were to force a Game 5, Rivers added: "I don't know. I can't answer that, but I'm not sure.

"From my understanding, they checked his knee out right after the game because he was complaining about some soreness behind the knee, which is always a scary thing to hear about with players. 

"There was swelling already, which is way too early, so we did the MRI. As a coach, I hate that word. I hate those three letters, because it never comes out well. 

"It just feels like that, whenever they tell a coach you're going to get an MRI, it doesn't turn out well most of the time, and this time it did not."