SAN FRANCISCO (AP) — Clay Matthews and the Green Bay defense spent a good chunk of the offseason focused on figuring out how to stop the read option and defend mobile quarterbacks like San Francisco’s Colin Kaepernick.Kaepernick left that much of a mark on the Packers’ embarrassed unit in a 45-31 divisional playoff loss to the 49ers at Candlestick Park in January. Now they meet again in a second straight season opener between a pair of NFC powers.“I’m sure they’ve been game-planning for us since training camp,” 49ers tight end Vernon Davis said. “Any time you lose a game like that, you should be very mad.”Kaepernick rushed for a quarterback-record 181 yards and two touchdowns and threw for two more TDs.The Packers have been forced to relive the game in the film room this week — even if many of Green Bay’s players weren’t part of it.“It was a disappointing night for us,” quarterback Aaron Rodgers said.Kaepernick, for one, has vowed to forget about that impressive playoff debut eight months ago.“We’re not worried about what happened last year,” he said.The Packers have no choice but to be worried.