GREENSBORO, N.C. – The most intriguing training camp competition during Celtics camp appears to be the battle for the one remaining roster spot between swingmen James Young and R.J. Hunter.

Young, in his third NBA season, has impressed so far with his confidence and scoring ability. He scored 7 points on 3-for-3 shooting in the Celtics’ 92-89 loss to the Philadelphia 76ers on Tuesday in Amherst.

Hunter, meanwhile, not only went scoreless in eight minutes with two turnovers, he was scorched defensively by 76ers reserve Brandon Paul, who sparked Philadelphia’s second-half comeback with 15 points in 13 minutes. While preseason game performances aren’t critical for most players, the Celtics are closely evaluating the progress of Young and Hunter.

The club has 16 players on guaranteed contracts but can only break camp with 15 players, so the next few weeks could be critical for both players. Celtics coach Brad Stevens has lauded Young so far for his training camp performance and defended Hunter after a difficult debut.

“I think R.J. had a really good offseason, really prepared,’’ Stevens said. “And the one thing he’s struggled with in the first couple of days is making shots and that’s usually the case when you’re going harder and there’s more wear on your legs. So I’m not overly reacting to that. That’s a small sample size. We know what he’s about. We know how good he is. We know he passes the ball and can shoot the ball. And he’ll play better.’’

Getting in the flow

Center Tyler Zeller is coming off a difficult season, his playing time having been slashed to 11.8 minutes after logging 21.1 and a career-best 10.2 points in 2014-15.With the team’s plethora of big men last season, Zeller lost minutes.

Those are minute’s he’s trying to regain this year as part of the second unit. The Celtics’ bench struggled mightily in Tuesday’s loss.

Zeller finished with 6 points, 7 rebounds, and 3 assists in 20 minutes as the primary backup to Al Horford and Amir Johnson. Zeller began as a starter last season then quickly lost his slot to Jared Sullinger, the beginning of a disappointing season.

“I’m just trying to do whatever I can, obviously last year wasn’t the year I wanted,’’ Zeller said. “I’m just trying to get off on the right foot.’’

The second unit right now consists of Zeller, Marcus Smart, Terry Rozier, Jonas Jerebko, and rookie Jaylen Brown. The reserves struggled mightily from the field until the waning minutes against the 76ers, relinquishing a double-digit lead, but they are still trying to establish chemistry and get accustomed to new roles, such as Rozier, who is the new backup point guard.

“Terry is somebody new that I’m working with,’’ Zeller said. “But I really enjoy working with him, trying to slowly get on the same page. I think it’s coming along well.’’

Stevens said getting good shots was an issue for the second unit.

“I just didn’t think that they found the best shot for their group,’’ Stevens said. “I think that’s what they have to do. Part of that is learning and growing together, figuring each other out. There’s a bunch of young guys, Jaylen is new, Terry is still young, Marcus is still young. Tyler and Jonas didn’t play a ton together last year. So it’s just learning the different guys. I feel good about what they’ve done through the preseason but [Tuesday] wasn’t their finest hour.’’

Gary Washburn can be reached at gwashburn@globe.com. Follow him on Twitter @GwashburnGlobe.