Opportunity knocked and the Flyers, once again, were making a line change. Now at the halfway point of the season, everyone in the dressing room who was asked to assess the first 24 games pointed to little mistakes. They’re mental ones according to defenseman Kimmo Timonen, and Tuesday night they came in the third period. Both the third and fourth Rangers goals in New York’s 4-2 win over Philly last night came when the Flyers were trying to change personnel. “Those things should be easy to fix,” Timonen said. “Sometimes it’s reading the play, sometimes it’s a turnover that causes a bad change. It caused the game today.” Behind the bench, coach Peter Laviolette was fuming over it. “There’s been too many of them,” Laviolette said. “Too many discussions and too many topics about the line changes. It needs to be executed and it’s not.” Make it six consecutive times the Flyers have lost at Madison Square Garden. Were it not for mental errors, they could have come out with a victory to end the first half of the season. “That can’t happen,” said Wayne Simmonds. “You’ve got to keep the game simple, maybe keep one guy out there or something like that. That was the difference.”