SAN FRANCISCO – Warriors coach Steve Kerr during his pregame news conference Friday identified the greatest threat to the success of the team this season: Turnovers. When they commit fewer, they win. When they commit more, they lose.“That’s our No. 1 concern at this stage,” he said. “Seventeen games in, it’s pretty clear what we have to do. If we take care of the ball, we win. If we don’t, we lose.”Four hours later, in Game 18, at Chase Center for the first time since Nov. 9, the Warriors committed fewer giveaways than the Portland Trail Blazers – and, for the first time this season, lost.Lack of size and interior muscle is an issue that has surfaced all too often this season, and they were the primary cause of the Warriors walking off the Chase Center floor with a 127-123 lashing that killed their homecoming buzz and dropped them back to .500.“We know we’re small out there at times, but we got to play bigger than we are,” said Stephen Curry, whose game-high 38 points went for naught. “There were a lot of breakdowns and missed box outs because they had five out most of the time, with a 7-footer in there....