WALTHAM, Mass. -- Chris Johnson embarked on what could be his final road trip with the Boston Celtics on Tuesday as the team trekked to Philadelphia in advance of Wednesday's tilt with the 76ers.

The Celtics must soon decide if Johnson, whose second 10-day contract expires on midnight Thursday, will be signed for the remainder of the season. There's certainly interest on Boston's end given the way he's performed, but the lingering trade deadline and a need to maintain roster and salary cap flexibility is working against Johnson.

The Celtics essentially have two open roster spots, but those could come in handy before Feb. 20. The bigger issue is leaving enough financial flexibility to navigate the deadline. By our rough calculations, the Celtics are currently hovering around $70.6 million committed in luxury tax calculations. That's a little more than $1 million from the $71.75 million tax line that Boston has absolutely no desire to step over this season.

Committing to Johnson for the season as early as Friday would, by our rough estimate, cost Boston about $320,000 in salary. If the Celtics make no other moves, that's not a prohibitive number, but it's a lot easier to stomach after the deadline when Boston's finances would be a bit more certain.

The question for the Celtics is whether they like Johnson enough to risk losing him when he becomes a free agent on Friday, or are they confident enough they can get him back later in the year? Signing him to a future-minded deal later in the year would minimize the salary commitment and keep him in the program through the summer with nonguaranteed money for future seasons.

"We have not talked about it in finality or final details," said Celtics coach Brad Stevens. "But I do know it’ll be a decision of can we afford to do it from a cap management and all that stuff standpoint, but I don’t really understand the exact details of that. If we decide not to re-sign him, it won’t be because of anything that would be basketball related from the standpoint of his performance. I think every one of us would love to have him in the program for all that he’s meant at this point and time, just in the last 20 days. He’s been fantastic."

Stevens admitted it's a unique situation not to have control over whether a player stays or goes, but said he'll ultimately defer to president of basketball operations Danny Ainge and his staff.

"My job is to give my opinions when asked on it," said Stevens. "At the end of the day, the most important thing for our program long term is to let those people make decisions and to trust that those are the right ones. Because I do trust them, they’ve done a great job with that in the past and Danny and his group know exactly what they are doing. I think the hardest thing for Chris is he’s just gotta realize that he can control what he can control. Hopefully he’s around here, but if he’s not, I don’t think by any means it will be the last time you see him. I think he’s going to have a nice career in the NBA."

Johnson, who has averaged 8.7 points, 3.1 rebounds, 1.4 assists over 24.1 minutes per game over seven appearances, seems to understand his situation.

"All you can do is control what you can control, take it a day at a time, try to get better, put yourself in the best situation for guys to decide whether to keep you or not and go from there," he said after practice Tuesday.

Johnson said he hasn't talked with the team about his future and is just focused on finishing out this current 10-day pact strong. He's hoping that if things do not work out here, maybe his play will have raised some antennas around the league.

"Hopefully I've put myself in the best situation with eyes open on other teams and just go from there," said Johnson.

There's at least one important Johnson supporter in Boston's locker room: Captain Rajon Rondo.

"Hopefully we can sign him for the rest of the year," said Rondo. "He's shooting the ball, shooting it well. He's being very professional. Always on time. And he's producing in the game."

Read on for more practice notes, including a well-rested Gerald Wallace, Rondo on the Seahawks bandwagon, and Kris Humphries vs. Jerryd Bayless in 1-on-1.