The NHL is already making tweaks at the start of preseason play, according to an ESPN.com report. Some of the initiatives from last month's research and development camp debuted Monday during a game between the Maple Leafs and Senators. Among the changes is a green verification line that runs 3 1/4 inches behind the goal line and shallower nets that feature thin mesh along the top and a clear plastic skirt along the bottom. The proposed tweaks are intended to make it easier for the league's video room to make correct calls using instant replay.