LAS VEGAS — Minutes after Morez Johnson Jr. made his NBA Summer League debut Thursday, a current teammate and a former teammate took separate turns crashing his postgame news conference.First, Dallas Mavericks forward Cooper Flagg butted in to congratulate Johnson on his near double-double.Then Yaxel Lendeborg — the Golden State Warriors rookie who won a national championship alongside Johnson at Michigan in the spring — interrupted to ask Johnson about getting to face each other.“I tried to big boy him,” Lendeborg said after the Warriors’ 101-90 win over the Mavericks. “Never worked.”If Thursday’s game was any indication of how his first NBA season will go, Johnson is going to be a formidable presence inside. The 20-year-old, who grew up near Chicago, scored 27 points, collected eight rebounds and notched three steals and two blocks. His two-way impact allowed the Mavericks to at least make the game competitive — cutting Golden State’s lead down to 3 with four minutes remaining — after they fell behind by 24 points.“He’s relentless,” Lendeborg said about Johnson. “It seems like he never gets tired. He’s just a strong human being. It’s just ridiculous. He’s going to be a monster in a few years. Maybe this year, too.”