Reggie Evans has made it his mission to improve Brook Lopez’s game this season. And now, as Evans and the Nets prepare to kick off their first postseason as Brooklyn’s team tomorrow against the Bulls, he said he thinks his protégé is ready for his first taste of playoff basketball. “Man, look at Brook,” Evans said after yesterday’s practice. “He’s probably, what, a top two big man? Brook’s shown you everything [this year]. “He’s a whole different person right now. … Ain’t nobody stopping him. The only person that can stop Brook is Brook. That’s it.” If the Nets are to advance out of their difficult matchup against the Bulls in the opening round of the playoffs, they’re going to need Lopez to be at his best. In a series that is sure to be a grind-it-out, physical series full of half-court basketball, thanks to the slow and steady way both teams play, Lopez will be the most talented offensive big man on the floor. His game has made big strides this season, one in which he led all NBA centers in scoring at 19.4 points per game, shot better than 52 percent from the field, blocked more than two shots per game and was selected to play in his first All-Star Game in Houston.