It seems like the NBA season only just started, but we're already about a third of the way through the 2017-18 campaign.

The calendar hasn't flipped to 2018 just yet, but there have already been plenty of exciting games, breakout players and intriguing storylines.

From the farthest reaches of the Eastern Conference all the way out to the West Coast, there have been plenty of surprises already this year.

Both good and bad, no one could have predicted some of these developments that have taken place in front of our eyes this year.

With two-thirds of the season left to go, there are sure to be more storylines and outstanding performances that will catch our attention.

For now, though, here are the five biggest surprises the 2017-18 NBA season has provided so far:

1. The Thunder struggling with new stars

Through 30 games, the Thunder were 15-15 and barely clinging to the eighth and final playoff spot in the Western Conference.

When OKC landed Carmelo Anthony and Paul George this summer, it was supposed to signal a run at Western Conference dominance, but instead, it has been difficult to work those two new stars (particularly Melo) into new roles alongside reigning MVP Russell Westbrook.

Whether or not the trio of stars figures out how best to play alongside each other will be the biggest storyline to watch as the calendar flips to 2018. We're either heading for greatness or chaos in Oklahoma City, with very little chance of a middle ground.

2. The Pacers not falling apart without Paul George

When the Pacers traded Paul George to the Oklahoma City Thunder for Victor Oladipo and Domantas Sabonis, many thought the Pacers didn't get enough for their star player.

However, as OKC has struggled (see above), the Pacers have actually thrived under Oladipo's leadership and improved play.

Through 31 games, the Pacers were 17-14 and in fifth place in the Eastern Conference playoff race, which no one would have expected after the PG-13 trade. However, the young Pacers have been exciting to watch and don't appear to be going away anytime soon.

3. The Celtics' 16-game winning streak

The Boston Celtics watched in horror as star forward Gordon Hayward went down with a gruesome leg injury only five minutes into his Celtics career.

Boston lost that season-opening game to the Cavaliers and then lost the next game against the Bucks. However, after that, new point guard Kyrie Irving and his teammates turned things around in a huge way, rattling off 16-straight victories to show that they are a team to be reckoned with in the Eastern Conference.

The Celtics have cooled off slightly since then, but still went 10-5 over their next 15 games and are definitely in the hunt for the No. 1 seed in the East. Irving is playing at an MVP level and the young Celtics are following his lead.

4. Lonzo Ball's slow start

When the Lakers selected Ball with the No. 2 overall pick in the 2017 NBA Draft, many expected greatness from the talented point guard right away.

While he's been a solid player for the young Lakers, he has struggled mightily with his shot and has been inconsistent at times.

There are still flashes of brilliance and no reason to think he won't become a solid NBA player, but he hasn't lived up to the hype, as many had him atop their Rookie of the Year lists heading into the season.

5. Chris Paul and James Harden playing so well together

The Houston Rockets have been the best team in basketball up to this point, with leading MVP candidate James Harden leading the way.

However, the addition of Chris Paul has also worked wonders for the Rockets, despite preseason concerns about how well they'd be able to coexist as ball-dominant point guards.

Those concerns have been put to rest, though, as the Rockets had yet to lose a game that both CP3 and Harden started as of Dec. 20. The Warriors should be very, very worried about the threat the Rockets can provide them this postseason.