The Boston Celtics had a peculiar off-season that was mostly a roller-coaster ride of ups and downs. It began with losing their best player, Kyrie Irving. Although that is a loss that will be tough to recover from, just about all of Boston was prepared for him to go, making it much easier to deal with. On the other hand, losing Al Horford in free agency was a shock to many and is a blow the Celtics are going to suffer from. He truly made the offense flow, stretched defenses out by opening up the floor, and led on and off of the court. Horford is the perfect guy for this team particularly because of its young core, and he is certainly going to be missed. 
In an effort to soften the blow, Danny Ainge signed all-star free agent Kemba Walker in July. He is someone who seems like he will gel just fine with the entire roster. He has a team-first mentality, which is the exact opposite of last year’s Kyrie Irving. However, usually when big changes are made to a roster, it can take a year or two before chemistry is developed and before the team can play at its full potential. 
Well, that is why the Celtics lucked out this off-season. Kemba Walker, Jayson Tatum, Jaylen Brown, and Marcus Smart all made team USA. Not only did they all make the roster, they are all getting valuable minutes and playing together. The team is 3-1 in four games played, and a Celtic has started in each of the four games. Walker is averaging 17 points per game, which is leading the team by far. He is on his game and is as locked in as he has ever been. Brown is averaging 11.8 points per game, and has really been the talk of the off-season. He looks like a new player out there; he is playing free, he is knocking down shots, and he is not afraid to drive to the hoop. The improvement of Jaylen Brown could ultimately end up being exactly what the Celtics need in this upcoming season. 
As for Tatum and Smart, they have had some success too. Tatum is averaging 8.3 points per game and is shooting well from behind the arch. Smart has been battling an injury this off-season so he has only played in three of the four games, but he has looked good so far. Per usual, his defense stands out and continues to look better and better. 
The bottom line is that the fact that these guys are all playing together, traveling together, and getting to know each other before the regular season even starts, is awesome. It is a huge advantage over teams like the Nets, the 76ers, and the Heat, all of which have acquired new players who have yet to play with one another. Although you should not put too much stock in their actual play on the court this summer, you definitely should pay attention to the cohesion between the four of them.