INDEPENDENCE, Ohio -- Tyronn Lue's cell phone buzzed early Thursday morning, hours before the Cleveland Cavaliers held their first official practice in preparation for an Eastern Conference finals matchup against the Boston Celtics.

It was a message from Lue's cousin Justin -- as in, Justin Tatum, the father of Boston Celtics youngster Jayson Tatum, who has helped carry the wounded Celtics to a place few expected when the postseason started, and now stands in the way of Cleveland returning to the NBA Finals for the fourth straight year.

"It's tough because you want to see him do well, but not against you," Lue said with a smile. "We just have to try to take him and be physical with him and not let him get easy baskets. He's going to score because he can post and he can put it on the floor, but we just have to try to take away his easy baskets as much as possible."

Lue is from Mexico, Missouri. Tatum is from St. Louis, a car ride of about 120 miles -- or two hours.

The 20-year-old rookie sensation used to make that trip all the time, going with his father to see Lue for barbecues and the annual July 4 fireworks show that Lue funds. That July event in Mexico carries special significance because it falls on the birthday of Lue's late grandfather, Tyrone, the familial tie that binds Lue and Tatum.

"Just seeing 'Little J' when he was six or seven years old and now to who he is today is crazy," Lue said. "Seeing the player he's become, we knew he was going to be good, but now he's at a whole new level. Now he's an NBA player and playing at a high level it's just good to see."

Just a few days ago, Lue was looking at some old pictures of a young Jayson Tatum, who was a fast, but small, little kid.

On Thursday, Lue and the Cavaliers were poring through film of the Celtics and Tatum, who has grown into a 6-foot-8 scoring force, leading Boston in that category in his first postseason run.

Lue isn't surprised that Tatum, thrust into the primary scoring role in the absence of Kyrie Irving and Gordon Hayward, has made it. Lue believed his distant cousin was destined for this future when he was 14 or 15. Seeing Tatum thrive on the game's biggest stage doesn't come as a shock either.

"He's never in a rush, he plays patiently and reminds me a lot of Paul Pierce when Paul first came out," Lue said. "He's not scared, he's not afraid and he's always been that type of kid," Lue said. "He wants these type of moments and he's taking advantage of it. With Kyrie and Gordon going down and him having a chance to play the minutes he's been playing, starting and playing in the playoffs the way he has, he's taken full advantage of it.

"But he's never been scared, he's never been afraid of the big moment. You can see that."

Tatum leads a balanced scoring attack. One of six Celtics averaging double figures in the playoffs, Tatum is scoring 18.8 points per night, up from his season average of 13.9.

In Boston's closeout win against Philadelphia on Wednesday, Tatum scored 25 points, extending his streak of 20-point games to seven. That's tied for the second-longest streak by a rookie in NBA history.

The one thing Lue can't believe? Being in this specific spot, having to coach and root against Tatum.

In simple terms, family stands in the way of an NBA Finals trip. Lue certainly doesn't plan on allowing himself to get caught up in that. His job for this round doesn't change, entrusted with putting together a game plan to slow down the surprising Celtics. That starts with pestering "Little J."

That's why Justin's text message Thursday included the popular "smh" abbreviation, which stands for "shaking my head."

The good news for Lue: He says he never taught Tatum any of his championship tricks and won't take any responsibility for the budding star with the offensive gifts to poke holes in Lue's defense.

"No, no. He got it from himself and his dad," Lue said.