The Boston Celtics opened the 2015-16 campaign on Wednesday night against the Philadelphia 76ers, but James Young will have to wait to make his season debut. 

Young, drafted 17th overall in 2014, was the only healthy player inactive for Brad Stevens. Jordan Mickey and Terry Rozier, two of the team’s June selections, begin the season ahead of Young in the race for minutes at the end of the rotation. R.J. Hunter also appears to have surpassed Young on the depth chart, but the rookie was too ill to be at the arena. 

“It motivates me to just keep working hard,” Young said after learning that he wouldn’t play. “I have to just keep getting better everyday; I’m a lot better than last year. Just keep working.”

Young, 20, is the youngest player on the roster, but age is relative. As he begins his second NBA season, his inexperience looks more like an excuse than the true reason he hasn’t gotten on the court. Marcus Smart, drafted sixth overall in the same draft, is just a year older than Young.

He was visibly shaken when the locker room opened to the media. After speaking for a little more than a minute with reporters, he disappeared into an auxiliary room where Stevens had previously entered. Young emerged a few moments later, parked himself at his locker and draped a towel over his face.

There is no question that the Celtics drafted Young expecting him to require some marinating, but if they expect him to develop -- into either a part of their future rotation or as a trade asset -- he’ll have to show what he can (or can’t) do against NBA competition.

His playing time was sporadic at best last season. He played 148 of his 332 minutes in February and quickly slid out of the rotation shortly after Isaiah Thomas was acquired. His only action after March 22 came in the season finale when he logged nearly 25 minutes as the Celtics lined themselves up for the postseason.

Young saw nearly twice as many minutes playing for the D-League’s Maine Red Claws. He started 17 games for the Celtics’ affiliate, averaging 21.5 points, 4.8 rebounds, 2.0 assists and 1.5 steals in 32.9 minutes per game. He flashed the shooting ability that made him a first round pick, shooting 44.2% on threes and 46.3% overall.

He hasn’t shot well at the NBA level, going 17-for-66 (25.8%) from three, but is that a result of tougher defenders, small sample size or not enough minutes to get in a rhythm?

When asked about Young’s playing time, Stevens made it clear that he has a lot of work to do in order to muscle his way into the rotation. The Celtics have a number of interchangeable parts on the perimeter and Young needs to improve both his ball-handling and defense to become more versatile.

“I think that James obviously is in a position where we have our five guys that are probably going to play a lot of minutes at the 1, 2 and 3,” the third-year coach said. “We still have Jonas [Jerebko] and Terry as well. So you’ve got really seven deep at those spots. When you boil it down to the wing, probably even more.”

The Celtics are young -- David Lee, 32, is the only player older than 28 -- and lack aging veterans (see: Wallace, Gerald) to eat wasted minutes over developing players like Young. More than half of the players that stand in the way of Young getting minutes were acquired after he was drafted.

You could argue that the Celtics haven’t given him a chance, but he clearly hasn’t done himself any favors in practice or during the preseason. If the depth in the 2014 NBA Draft wasn’t so unimpressive, using the mid-first round pick on a player that his contributed nothing would be even harder to swallow.

“I’ve got to try to work on defense. That’s the main thing. This offseason, the preseason and the season coming up, working on defense. That and, I guess, being more aggressive on offense,” said Young of what he needs to improve upon.

Young told the media that he doesn’t know if the Celtics plan to dispatch him to Maine this season, but that certainly seems to be the path he’s on. Stevens was happy with the reports he received from the Red Claws last season and said numerous times this summer that Young has “made strides.”

He won’t turn 21 until next August, but in NBA years Young is getting old quickly. Ideally for Ainge, he’s either a future rotation piece or a trade chip -- right now he doesn’t look like either. His rookie contract includes two more team options and potential restricted free agency in 2018.

If nothing else, Young’s rookie season prepared him for what may lie ahead in 15-16.

“I had some bumps, some ups and downs, and now I know I’m going to be having some ups and downs,” he said. “I’m just going to keep working through it.”