Typically, when star players return from injury in the thick of a playoff race, they don't have much time to reacclimate themselves to the flow of the game; they're expected to be themselves off the bat.
Jayson Tatum does have that luxury though, as we've learned in his first few games back for the Boston Celtics. Tatum has scored between 20 and 24 points in his past five games, which is pretty impressive coming off an Achilles tear. There's also no reason for him to force himself to be the MVP candidate version of himself that he is when healthy.
This team was already great without JT; so easing back to full strength (which he's clearly not at yet) isn't going to derail what the team has built this season. In other words, a good version of Jayson Tatum is better than any other role player, and the Celtics have enough firepower to ease him back instead of force him back into his superstar role.
Jayson Tatum doesn't need to be a superstar immediately
When the playoffs roll around, the Celtics will need Tatum to be the fullly unlocked Jayson Tatum. Without that, the Celtics are probably an Eastern Conference Finals caliber team. With the real Jayson Tatum, they're probably the favorites in an Eastern Conference where no one wants separate themselves.
The team is 4-1 in its past five games that Tatum has played. In other words, him getting back into form isn't slowing the Celtics down at all; he's assisting the wins already, in fact, which is pretty remarkable for someone who hasn't played in nearly a year.
Cade Cunningham has (very sadly) been diagnosed with a collapsed lung, a scary non-sports injury. Detroit being down its best player does leave the top spot in the East up for grabs, though, and the Celtics are currently 3.5 games behind claiming it for themselves. If Tatum continues to trend upwards in his return, winning the East is up for grabs. But that shouldn't be the objective over the next month. The objective has to be winning the NBA Finals, and if that means not going full tilt to win the East, instead letting Tatum progress at his own pace, then so be it.