The success --or lack of -- for both teams in 2015 has centered largely around quarterback play.

Aaron Rodgers looks like the MVP of the league (again) after three weeks, guiding an injury-riddled Green Bay Packers (3-0) squad to a perfect record thus far.

For the San Francisco 49ers (1-2), their performance over the last two weeks have erased any memory of their season-opening win. In particular, Colin Kaepernick struggled mightily in Week 3 against the Cardinals, throwing four interceptions -- including two that were returned for touchdowns.

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Here are three keys to the game for both the Packers and 49ers.

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PACKERS

1. Contain Kaepernick in a prove-it game on defense

The Packers appear to have turned over a new leaf on defense, but they'll have to prove their new identity in Week 4. Kaepernick has made a habit of torching Green Bay's defense. In three career starts against the Packers (including two playoff wins), Kaepernick has thrown for over 900 yards and six touchdowns. He has also rushed 30 times for over 300 yards.

2. Keep San Francisco's pass-rush away from Rodgers

The Packers must afford Rodgers plenty of time to throw by keeping San Francisco's hungry pass-rushers at bay. The 49ers have six different players with a sack, so the pressure can come from anywhere. Linebacker NaVorro Bowman is back at full force after missing the entire 2014 season with a knee injury; Green Bay's blockers must be wary of him coming on a blitz.

3. If leading, don't let the 49ers hang around

Dating to the NFC Championship game, the Packers have been forced to field -- or try to field -- an onside kick in three of their last four outings. Green Bay looks like a dominant team, but the Packers haven't been able to win without late-game heroics. The 49ers have rolled over and lost by a total of 65 points over the last two weeks; this is a team the Pack can finally blow out.

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49ERS

1. Take the QB and run

The 49ers are bent on converting Kaepernick into a pocket passer, but as last week's four-interception debacle at Arizona showed, it's a work in programs. Kaepernick has won all three career meetings against the Packers and his legs have been instrumental in his success - he set a postseason record for rushing yards by a quarterback with 181 and a pair of TDs in the 2012 playoffs. He also riddled Green Bay for 412 passing yards in the 2013 season opener before ending the Packers' season four months with 98 yards rushing in another postseason victory.

2. Avoid another big early hole

Running back Carlos Hyde rushed for 168 yards and a pair of scores in a season-opening win over the Vikings, but the 49ers have been unable to follow that blueprint the past two weeks. San Francisco fell behind 29-3 at halftime in Pittsburgh in Week 2, effectively taking Hyde out of the game. A similar scenario unfolded last week as Kaepernick had two interceptions returned for TDs in the first six minutes as the 49ers found themselves staring at a 31-7 halftime deficit at Arizona.

3. Slow Randall Cobb at the pass

Ben Roethlisberger and Carson Palmer eached carved up the 49ers' secondary and have done so by focusing on their respective No. 1 receivers. Pittsburgh's Antonio Brown had nine catches for 195 yards and a touchdown while Arizona's Larry Fitzgerald had a field day with nine receptions for 134 yards and a pair of scores. If form holds, the Niners must find a way to contain Randall Cobb, who was on the receiving end of three touchdown passes from Rodgers on Monday night.