Associated Press About 19 hours after saying the Nets would make their regular-season debut tonight at Barclays Center against the Knicks, the NBA on Wednesday accepted Mayor Michael R. Bloomberg’s recommendation that the game be postponed because of Hurricane Sandy’s lingering effects on the public transportation system. “The bottom line is that there is not a lot of mass transit,” Bloomberg said at a news conference at City Hall. “Our police have plenty of other things to do.” The league’s initial optimism — expressed Tuesday in a tweet that said, “Knicks-Nets game will be played as scheduled this Thursday at 7 p.m. — followed hopeful remarks by Bloomberg earlier that day when he said he hoped that the game would be played and that he expected to attend. Adam Silver, the NBA’s deputy commissioner, said in a telephone interview that the Twitter message was sent out because “at that moment, the game was on. Games are on until they’re not.” He added: “At that moment, none of us thought there’d be so little mass transportation this far into the week.” But expectations that the game would proceed were eventually overwhelmed by the city’s assessment of the subway and rail obstacles created by the hurricane. Barclays sits atop a mass transit hub that is intended to reduce car traffic. But commuting fans would still find it difficult, if not impossible, to reach their local subway and Long Island Rail Road stations, some of which were flooded or damaged by the devastating storm.