Duke basketball began the new season with high hopes largely thanks to the arrival of a top recruit from Chicago. Through the first half of the season, the player had lived up the substantial hype and looked like a no-brainer choice at the top of the NBA draft after one season in Durham. Duke's offense was ranked in the top five of the country thanks to the considerable contributions of this player, but there were troubling signs to those monitoring the Blue Devils closely.

Mostly: Duke's defense was slipping, and it was partly because this Chicago native with heavy legs in the front court wasn't as effective on that end of the floor.

This could be a story about Jabari Parker, the No. 2 pick in last year's draft who spent his lone season with the Blue Devils captivating audiences with pro-ready offensive moves. You know how that season ended: Duke fell in its first NCAA Tournament game to a Mercer team that NaeNae'd its way into the hearts of America. The worry for Duke right now is that this season could be playing out the exact same way.

Jahlil Okafor and Jabari Parker are far from the same player, and admittedly some of the similarities up top are circumstantial. Parker is either a wing or a stretch four, while Okafor is your classic back-to-the-basket big man. There's a noticeable difference in having the 6'11, 270-pound Okafor in the middle of the Blue Devils' defense rather than the 6'9, 210-pound Amile Jefferson, who moonlighted as Duke's center last season.

Duke's defense is definitely better than it was a year ago, but it remains unclear if it's good enough to take Coach K on another deep tournament run. Last season, Duke's defense ranked No. 116 in the country, per KenPom. It's up to No. 55 this year. Most of the improvement can be traced to a lack of fouling. Opponents' free-throw rates have fallen from 40.8 percent last season (No. 177 in the country, per KenPom) to 24.1 percent (No. 3 in the country) this season.

The improvement is nice, but it won't mean much if Duke fails to get out of the first weekend of the tournament again. The defense remains far from a finished product. The Blue Devils have given up over one point per possession in seven of their last eight games. That includes surrendering 1.24 points per possession in a loss to N.C. State, 1.22 PPP in a loss to Miami and 1.13 PPP in a loss to Notre Dame.

In the middle of it all is Okafor, who has unquestionably emerged as one of the top players in the nation. He's in the mix for the Player of the Year award mostly because he's unstoppable on offense, posting an effective field goal percentage (65.2) which ranks No. 15 in the country.

Okafor's defense is another matter. While he's not terrible on that end of the floor, he's not particularly good, either. Draft Express did a great job of breaking down his strengths and weaknesses defensively:

While Okafor's defense will be the key to Duke's Final Four hopes this season, it carries even greater interest as the NBA draft approaches.

Okafor has been ranked as the No. 1 player in the draft by ESPN's Chad Ford since before the season started. He remains there today. On Thursday, in a story on how Okafor would potentially fit every team in the lottery, Ford wrote "As of today, every team I spoke with has Okafor as the No. 1 pick."

Perhaps this is easy to believe. There hasn't been a big man to enter the league as offensively polished as Okafor in a long time. Much like his friend Parker a year ago, Okafor has an incredible amount of offensive moves for a player his age. He's a great offensive prospect. The question is how much a great offensive center really matters in today's NBA if he's not giving you much defensively.

Okafor will remind you of a '90s big man on the low block with his constant variety of pivots, hooks and scoop shots. He's also an incredible passer. The rules are different now than they were in the '90s, though, and few elite teams are carried by post scoring. Conversely, nearly every elite NBA team has a great defensive big man.

You can go up and down the standings. Golden State is always thought to be defined by its offense, but it also has the No. 1 defense in the NBA. When center Andrew Bogut has been out, the Warriors don't look like the same title contender. Memphis has been carried by the stout defense of Marc Gasol, Houston has Dwight Howard, Portland has Robin Lopez, the Clippers have DeAndre Jordan, the Mavericks re-acquired Tyson Chandler to fix a poor defense last season.

If you're skeptical of how important rim protection is in the NBA, just look at what's happened to the Cleveland Cavaliers since they've acquired Timofey Mozgov. Twelve consecutive wins later, things don't look so bad for LeBron James' team anymore.

In the modern NBA, defense sure seems more important than offense for a center. The post-ups of the '90s have been replaced by ball movement, three-point shooting and off-the-ball cuts. It's a different league with different rules and different demands out of its stars.

This isn't to say Okafor will be a minus defensively forever. The man is 18 years old. He's blessed with incredibly long arms (7'6 wingspan) and is plenty athletic. He doesn't have great lateral quickness and his ability to corral ball handlers on the pick-and-roll is in question at the college level, let alone in the NBA. Still, he could turn himself into a solid defensive player a few years down the line. It's happened to DeMarcus Cousins this season. The team that drafts Okafor just has to know it may be a work in progress.

In the immediate, Okafor will be the key to Duke's tournament hopes on both ends of the floor. In the future, his ability to improve his defense will go a long way towards deciding how great of a player he ends up being in the NBA. No one enters the NBA after one year of college as a finished product. For as good as Jahlil Okafor is with the ball in his hands, that remains the case for him, too.