SANTA CLARA, Calif. -- Quarterback Colin Kaepernick had his worst NFL game against the Carolina Panthers two months ago.But that might not be what most concerns the San Francisco 49ers heading into their divisional playoff game at Carolina on Sunday. The game against the Panthers was just part of the problem. Kaepernick struggled against the league's better defenses in general throughout the 2013 regular season.Against the teams ranked in the top half of the NFL in Opponent Total QBR, Kaepernick led the 49ers to a 3-4 record.