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Here are 19 things for Celtics fans to watch for in 2019. Happy new year.

■   Al Horford’s knee: Horford missed seven games in December because of patellofemoral pain syndrome, a condition caused by damaged cartilage under the kneecap. The Celtics said they were erring on the side of caution, and that their primary goal is to have him healthy when he is needed most.

Horford has played well since his return and has had no issues with the knee, but he will be 33 in June, and that condition could return. Look for the Celtics to steal occasional rest games for Horford.


■   R eturn of Aron Baynes: Even though the center averages just 14.2 minutes per game, his absence due to a broken left hand is significant. The Celtics have outscored opponents by 10.9 points per 100 possessions when Baynes is on the court, the team’s top net rating.

In recent losses to the Bucks, Rockets, and Spurs, Baynes’s absence was glaring, as opponents feasted inside. Baynes was expected to be out four to six weeks, and he is almost at the two-week mark, so he should be back soon.

■   Jabari Bird situation: There appears to be no imminent resolution to Bird’s case. The second-year guard was arrested on domestic violence charges Sept. 8, and recent months have mostly just brought court appearances resulting in more court appearances. Bird’s next one is scheduled for Jan. 30. Look for the Celtics to part ways with him whenever the case is finalized, opening up a roster spot.

  Anthony Davis and the Pelicans: Last season, Davis led New Orleans to the Western Conference semifinals. The team hoped the upward trend would continue and Davis would then re-sign on a super-max extension this summer.


But New Orleans is just 17-21, and the belief around the league is that Davis ultimately will inform the Pelicans that he does not intend to re-sign, all but forcing them to seek a trade. If that happens, the Celtics will be one of the first teams at the door with their pile of shiny assets.

■   Warriors games! The Celtics and Warriors were once viewed as the two teams most likely to meet in this season’s Finals. Both have sputtered, although Golden State’s Finals track does not appear to be in great danger.

The Celtics, meanwhile, have two great opportunities to remind everyone why they were once Eastern Conference favorites. The teams will meet at TD Garden Jan. 26 before a rematch in Oakland March 5.

Regular-season meetings usually end up meaning more to the team playing against Golden State. But the Celtics have had success against the Warriors and earned their respect, so Golden State will take the challenges seriously.

■   But that’s not all: The Celtics recently completed a dreadful stretch of their schedule in which they played mostly lottery teams. But 2019 will be different. In addition to the two Golden State games, Boston still has three left against the Pacers and two each against the Lakers, Clippers, Raptors, and 76ers, as well as games against the Thunder, Bucks, Nuggets, and Rockets.

Related: Here is the Celtics’ remaining regular season schedule


■   Trade deadline: The NBA trade deadline is Feb. 7. With a talented roster and plenty of future assets, the Celtics don’t have an obvious need. There was a time when Marcus Morris, who figured to have a diminished role and will be an unrestricted free agent at season’s end, appeared most likely to be dealt. But he has been Boston’s second-most valuable player this year.

Terry Rozier will be a restricted free agent, but his value probably has dipped since last May, and he also will be an important part of any playoff run.

It’s never wise to believe that Danny Ainge will sit back and wait, but Celtics fans probably should pay more attention to moves by potential playoff opponents such as the 76ers.

■   Future draft picks: 2018 was not a great year for Boston’s future assets. The Celtics will receive the better of the Kings’ and 76ers’ picks as long as neither is No. 1 overall; they also will get the Grizzlies’ pick if it falls outside the top eight and the Clippers’ pick if it falls outside the top 14.

The Kings’ pick was viewed as the top asset, but Sacramento is 19-17 and clawing for a playoff spot. The Grizzlies are slumping but still 18-17. It’s actually good for the Celtics that the Clippers are good, but they would prefer that they fall a bit from the No. 4 spot in the West.

The guess here is that when all is said and done, the best pick of the lot will be the Grizzlies’ pick at No. 10 overall.


  All-Star weekend: At the start of the season, the over/under on Celtics All-Stars probably would have been 3.5. But the team has stumbled, and Kyrie Irving is the only player having a true All-Star season. If Boston gets a second All-Star, it would probably be Morris, but the Celtics probably will have to move out of fifth place in the East for that to happen.

■  But look for Kyrie to be All-NBA: Irving has been dominant. When he is on the court, the Celtics have outscored opponents by 10.2 points per 100 possessions. And when he sits, they have been outscored by 0.3 points per 100 possessions. He is the only player whose departure from games has resulted in a negative net rating.

Last season the team had a 5.2 net rating with him on the court and 2.2 with him off, a considerably more narrow margin than this year. Irving has been named All-NBA just once, when he was a third-team pick in 2015.

Related: ‘I told you my object is to heal the world’: Kyrie Irving explains why he gave money to homeless man

  Jaylen Brown’s consistency: The Celtics have been waiting for the third-year wing to snap out of his offensive funk. Every time it looks as if he has found a rhythm, he regresses. Consider: After averaging 21 points per game over a three-game December stretch, he followed by averaging 4 points in his next three. Perhaps this latest surge — Brown has made 20 of 30 shots in his last three games — will be sustainable.


■   Playoff matchups: Even though more than half of the season remains, the top five seeds in the Eastern Conference have been all but locked up. It would be stunning if the Raptors, Bucks, Pacers, 76ers, and Celtics did not occupy those spots. But there will be plenty of jostling for position.

As Boston showed when it was trampled in three opening-round road games against the Bucks last season, home court matters. It might be tough for the Celtics to grab the No. 1 seed, but their preference would be to at least secure home court in a conference semifinal matchup.

■   The defense: After the Celtics defeated the Pelicans Dec. 10, their 102.1 defensive rating was second in the NBA. Since then, though, they’ve been something of a sieve, allowing 111.6 points per 100 possessions, 20th in the NBA over a three-week span. Baynes’s return should help, but this team doesn’t have enough offensive firepower to let up at the other end.

Related: How Kyrie has become a better defender

■   Marcus Smart’s . . . 3-point shooting? He won’t be confused with Stephen Curry anytime soon, but Smart has quietly improved his 3-point percentages in four consecutive seasons, from 25.3 to 28.3 to 30.1 to 32.3 this year. If he can eventually settle in around 35 percent, the Celtics would be thrilled.

  Kyrie’s playing time: Irving averages 32.3 minutes per game, which ranks just 47th in the NBA. He said recently that he would like to play more and shoot more. And over the last seven games, he is averaging 34.7 minutes per game, which would be tied for 16th in the league.

■   The Raptors: Toronto’s success could be notable both this year and beyond. If the Raptors make the NBA Finals, Kawhi Leonard may think twice about signing with a Los Angeles team in the summer, and that would be bad news for Boston.

■   Isaiah Thomas’s return? Last season there was some awkward controversy surrounding Thomas’s return to Boston with the Cavaliers. The injured guard asked that his video tribute be postponed until he was playing, and then that game happened to be Paul Pierce’s jersey retirement day, and then Thomas was traded before it mattered.

Anyway, Thomas, who still has yet to play this season as he recovers from last March’s hip surgery, is scheduled to return to Boston with the Nuggets March 18.

■   Gordon Hayward’s return to form: It appears increasingly likely that Hayward’s 30-point, 9-rebound, 8-assist game against the Timberwolves Dec. 1 was an aberration. In his 11 games since then, he is averaging 8.6 points, 3.8 rebounds, and 3.5 assists while shooting 34.8 percent overall and 28.6 percent on 3-pointers.

With the season almost halfway over, it’s fair to wonder whether that is just what Hayward will be this season.

Related: Hayward preaches patience on the road back

  A two-way add: The Celtics waived two-way contract player Walt Lemon Nov. 29 and have yet to fill the slot. Given Boston’s roster depth, there is no urgency to add a G-League player who can spend a maximum of 45 days with the Celtics. But the Celtics will probably fill the spot to get a look at a young prospect.

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him on Twitter @adamhimmelsbach.