The Nets’ post-Brook Lopez era begins with their first preseason game, against the Knicks Tuesday night at Madison Square Garden, and coach Kenny Atkinson said he expects guard D’Angelo Russell, who was acquired in the July deal that sent Lopez to the Lakers, to make an early push to “prove he’s a pretty good player.” The 21-year-old Russell was quick to agree when he spoke to reporters following practice Monday. “Oh yeah, I think the first preseason game is an opportunity for me to lay my stamp on what I’ve been working on,” Russell said. “But more importantly with the team, I want to establish my role right away — just be aggressive and make things happen so guys know they can look to me and know they’re going to get that from me.” Atkinson admitted he’s anxious to see how the Nets’ style on offense will evolve with a smaller lineup that doesn’t revolve around the presence of the 7-foot Lopez. He liked what he saw from Russell during the Nets’ four intense training-camp practices last week at the U.S. Naval Academy. “I’ve been really impressed with the pace he’s been playing with at the offensive end,” Atkinson said of Russell. “And his defense, especially on the ball, has been pretty good. His off the ball stuff, he’s still got to clean up. He relaxes sometimes. But pleasantly surprised so far overall.” Russell and veteran Jeremy Lin are expected to form the starting backcourt, but Atkinson mixed and matched a variety of combinations on the perimeter during training camp. New shooting guard Allen Crabbe and second-year small forward Caris LeVert, both of whom suffered minor ankle sprains in training camp did not practice Monday and won’t be playing in the first of four preseason games.