Assuming that Lonzo Ball is taken by the Lakers, the Celtics will most likely choose between two small forwards: Josh Jackson or Jayson Tatum. As I have mentioned, if the Celtics did not pick Jaylen Brown last year, Josh Jackson would be a perfect fit in Boston (even with having the first overall pick). He would fit in with Coach Stevens right away.
Jackson and Brown are very similar in the fact that they are defensive-minded small forwards with fantastic athleticism. However, Jackson possesses a more versatile skill set than Brown. Jackson is also a terrific passer, and can bring up the ball/run the offense if needed.