Joel Embiid has no intention of waiting for the regular season to play in a game. He wants to play preseason basketball. Period. Alas, he is at the mercy of an overly cautious Sixers medical staff. “I trust them, but at the same time, I have a voice, too,” Embiid said Thursday. “I think they value my opinion. It’s about us being on the same page.” Right now, the page looks like this: Embiid was cleared for full-court, 5-on-5 action Thursday but will be held out of the Sixers’ second preseason game against the Celtics at the Wells Fargo Center on Friday. Coach Brett Brown said he wants to work slowly with Embiid so that he is ready to go for opening night Oct. 18 in Washington, but he isn’t ready to pinpoint an exact date. But is Embiid OK with waiting until opening night? “No,” he said. “I would like to play preseason because last year it helped me get in a groove … and to get back to the dominant player that I want to be.” Embiid acknowledged that he felt rusty Thursday after his first full practice since surgery on March 24 to repair a meniscus tear in his left knee. But from the portion of a practice scrimmage in Camden available to the media, he looked great.