Rajon Rondo, a fixture for every team moment this season, from practices to games, missed yesterday’s practice to honor a doctor’s appointment as he continues to recover from ACL surgery. According to a source, the Celtics point guard will also meet with his knee surgeon, Dr. James Andrews, somewhere between Dec. 7-10 in Pensacola, Fla. Rondo still needs clearance to take part in full practices. The Celtics are as quiet as ever about a Rondo timetable. “Even if it’s 100 percent, there aren’t other bodies on the floor,” coach Brad Stevens said of Rondo’s level of activity. “He’s been playing a little bit of one-on-one before games, but I haven’t seen a lot that would say he’s close to ready. I haven’t seen a timeline, or heard about anything in the near future.” But anecdotal evidence is starting to build that Rondo may be ready for an increase in activity. “He still has his quickness — he can still finish with either hand,” forward Jared Sullinger said. “Rondo is Rondo, and when that knee gets healthy, look out.” Said forward Gerald Wallace: “He seems to be moving better. His confidence is a lot better in his leg. We don’t want him to rush it or mentally come back when he’s not prepared. We want him to come back when he’s ready.” Though Stevens has made it his goal to have a system in place that will accommodate Rondo, that process, too, will take time. “It will be interesting. The main thing for us is how he fits in with us and the way we’ve been playing,” Wallace said. “What can he and can’t he do, mentally, with his knee? We don’t expect him to come back in the first game as the All-Star Rondo. We want him to take his time, and work himself back into the game and slowly become the player that he’s always been.” Sullinger empathizes Sullinger, who is only now rounding back into full basketball shape following his recovery from back surgery, has a special place in his heart for players like Chicago Bulls point guard Derrick Rose and Memphis Grizzlies center Marc Gasol. Chicago has lost the former for the year to his second knee surgery, and Memphis, which makes its annual Garden visit tonight, has lost Gasol for at least a month to a sprained MCL. “This game has done so much for so many people, and to see someone like Derrick Rose or Marc Gasol go out is really tough, especially for Derrick Rose, taking the whole season to get back and get his legs straight,” Sullinger said. “You have to be thankful. Seeing them get hurt made me more thankful that my back is OK, and I can play the game I love.” Sullinger has confidence that he has applied the proper mental approach to his return. “The toughest part coming back from an injury is actually mental, making a move and feeling that you’re OK,” he said. “I know where everybody is coming from. With my back, I was nervous for the first blow, nervous for the first charge. Everything was scary at first. I was more in shock when I hit the floor, but then I got back up. Mentally I thought I was hurt, but physically I wasn’t. Once I broke through that, I was fine. You go out there, you play hard and don’t think about it. That’s how I was brought up.”