Power forward for the Boston Celtics: Jayson Tatum
Age in 2029: 31 years old
Just as Jaylen Brown is an obvious choice, Jayson Tatum being in the dream starting five is just as obvious. He’s a perennial All-NBA First Team player, and by the time he’s 31 years old, he will be fully in his prime.
Barring a complete and utter disaster, Tatum will be on the team in five years. He’s the centerpiece of the franchise, and they will do everything possible to keep him around.
As things stand right now, Tatum is the only player who has a deal in place that runs through the 2029-30 season. He has a player option for that year.
Center for the Boston Celtics: Xavier Tillman
Age in 2029: 30 years old
People will want to put Kristaps Porzingis in this spot, but even in a dream world, his injuries probably wouldn't let him play consistently at 34 years old. Even if he's on a team, expecting him to start the majority of the team's regular season games is unlikely.
Of the bigs on the current roster, Xavier Tillman seems like the best long-term fit to replace the Al Horford-type of center, which is a great fit with this starting five.
Tillman has already proven to be a very valuable player, as he played crucial minutes against the Dallas Mavericks in the NBA Finals. He’s a stellar multi-positional defender, and if his three-point shot comes around, he could be a quality starting option.
Boston just signed Tillman to a new contract this summer, but it’s only for two years. So, if they want to keep him around, they’ll have to work something out on a more long-term basis.