The Celtics have set the league on fire after starting the season off 0-2. The C's have won 15 straight games thanks to their stifling defense, the surprise contributions of young guns Jayson Tatum and Jaylen Brown, and the wizardry of head coach Brad Stevens.

Despite the hot start, this team still has obstacles in its way, ones that will prevent them from holding up the Larry O'Brien trophy in June.

1. LeBron James/Isaiah Thomas

Even during his 15th season, The King is still going strong, averaging 28.9 points on 58% shooting, 7.8 rebounds, and 8.6 assists per game. Somehow, this is the LeBron that's saving his energy for April and June.

When the playoffs roll around, James will unleash an even more dominant version of himself. Jaylen Brown is a nice young player, but he simply doesn't have the experience necessary to stop such a high IQ player like LeBron.

LeBron James
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Then there's Isaiah Thomas, who the Celtics traded last August in order to obtain the services of Kyrie Irving.

Assuming he makes a full recovery from his hip injury, Thomas is going to be on the war path. If these two teams face off in the playoffs, Isaiah will be on a mission to prove to the rest of the league that he's still an elite point guard, while making Celtics GM Danny Ainge regret trading him.

After being doubted his entire career, this man doesn't need any extra motivation. But to see how he plays with a little extra juice will be fun to watch, but extremely difficult to defend.

Despite their great defense, a pissed off Isaiah Thomas and the usual greatness of LeBron James would be too much to handle for the Celtics.

2. Lack of scoring

With the loss of Gordon Hayward so early in the season, a gap emerged in the Celtics offense.

Hayward was coming off a season in which he averaged a career-high 21.9 points per game. That scoring was supposed to be a part of the Celtics offense, and now it's gone, without a viable replacement.

Al Horford is more of a jack of all trades type of player, while the rest of the Celtics roster isn't capable of consistently taking some of the scoring burden off Kyrie Irving.

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Nobody outside of Kyrie can consistently create their own shot. Come playoff time, defenses will tighten up, and teams will have to rely more on individual creativity instead of set plays. Without any true scorers on the team besides Irving, the Celtics are going to have a difficult time putting the ball in the basket, something that's already much harder to come by in the postseason.

3. Only one star player

Gordon Hayward's injury didn't just leave the Celtics without a scoring punch, it shifted more of the scoring burden onto Kyrie Irving.

Teams that revolve around a single star player can have great success in the regular season. Opponent's defenses are more lackadaisical, and there isn't much scouting done beforehand.

Once the playoffs start, teams face off a minimum of four times. This gives each team more time to scout their opponents, allowing them to identify their weaknesses and exploit them.

When teams face the Celtics in the playoffs, it's going to be a repeat of what opponents did last season to Isaiah Thomas. They're going to take the ball out of Irving's hands and force the other guys to beat them.

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Jayson Tatum has been phenomenal so far this season, averaging 13.9 points per game. Down the line, he could end up being a great scorer in this league. But he's only in his first season, and to expect him to up his game in the playoffs is unrealistic.

If guys like Al Horford and Marcus Smart can force the defense to plan for them, the Celtics will have a shot to make a Finals run. But those guys have never been adept at scoring in bunches. It's highly unlikely they'll start come postseason time.