NBC’s baseball coverage starts to hit its stride this week as “Sunday Night Baseball” begins its summer stint on the network’s primetime schedule. Beginning with Sunday night’s NL Central matchup between the Chicago Cubs and St. Louis Cardinals, there will be a game on NBC every week until Labor Day. The only exception is July 12 because of the start of the All-Star break. NBC will also have a game on Labor Day between the Cardinals and San Francisco Giants. The network will have the Wisconsin-