The 49ers began 2013 with a rousing victory over the Packers – and then crashed to earth the next week in a 29-3 loss at Seattle.It's been that kind of a year for the 49ers, who've been up one week and down the next and had problems against good teams. This season, in fact, San Francisco has just one victory aginst a team with a winning record (the Arizona Cardinals).That Week 2 loss to the Seahawks still stings. Niners safety Donte Whitner says he and his teammates are motivated to come up with a big game Sunday at Candlestick when the 49ers (8-4) host the Seahawks (11-1)."They embarrassed us last time we were there," Whitner told Matt Barrows of the Sacramento Bee this week. "The quarterback (Russell Wilson) likes to run around and make plays with his feet. They have one of the best running backs in the National Football League (Marshawn Lynch). But we feel like we'll be ready for the test, and it's going to be a really, really big game and we're looking forward to it."In order to come up with a victory over the NFC West leaders, however, the 49ers have two big tasks. First, stop the Wilson-led offense. Second, score points on one of the NFL's best defenses.Wilson, in his...