GREEN BAY – It’s the last quarter of the first quarter.

Mike McCarthy likes to break down a season into fourths, which means the first quarter of 2015 wraps up on Sunday with the Packers’ fourth game, in San Francisco.

In his repeated emphasis on a fast start, McCarthy said after Monday night’s third win and again on Wednesday that going undefeated in quarter one would achieve the goal.

His players have heard him.

“4-0 is a fast start, so we’re trying to get this win this week,” veteran receiver James Jones said.

That narrow focus has relegated thoughts of four straight losses to the 49ers, the last of which was nearly 21 months ago in the 2013 playoffs, to the back burner at best.

The Packers also aren’t thinking about walking into the same venue, Levi’s Stadium, where they’d like to end their season, as Levi’s is the site of Super Bowl 50.

“When we go out there this week, we’re solely focused on trying to get this one win,” Julius Peppers said. “We’re taking this thing one step at a time.”

Added quarterback Aaron Rodgers: “It’s Week 4. That’s what I’m thinking about.”

Of course the rest of the Packers’ opponents, beginning with the 49ers, are thinking about how to slow down the two-time league MVP as he runs an offense as efficient as it is dangerous.

Rodgers is completing just under three-fourths of his passes (73.6 percent), has been sacked only three times and has not thrown an interception as the Packers have averaged 32 points per game. His passer rating of 135.4 is the highest in his career after the first three games by nearly 15 rating points (2011, 120.9).

“I think (backup QB Scott) Tolzien said it best the other day: It’s like watching Michael Jordan in his prime,” Jones said. “Every time you go out there the dude does something special. Like I’ve been saying these first three weeks, we’re all witnessing something special.”

Rodgers appreciated but deflected the praise, saying he’s “not worthy” of comparison to a player like Jordan, of whom he was a big fan growing up.

He preferred to compliment his offensive line for the low sack number, calling the pass protection the best in his eight seasons as the starter.

“That’s as big a tell of how we’re playing on offense as anything,” he said.

His teammates, meanwhile, have no trouble marveling at what they’re seeing. From drawing defenses offside and gouging them with free plays, to scrambling for first downs, to throwing pinpoint passes from the pocket on wheel routes up the sideline, Rodgers is doing it all as well as anyone can do it.

“It’s all I’ve been accustomed to here,” said Clay Matthews, who came to the Packers in Rodgers’ second season as the starter, back in 2009. “It’s not that I take it for granted, but we expect it.

“Then you watch some of these other quarterbacks around the league, and (you think), ‘How can they not hit that throw? How can they not do that?’ People can take it for granted, but it’s what we’ve come to expect. Stellar play.”

The Packers defense has been at the same level at times. The fourth quarter against Seattle was outstanding. The first 2½ periods against Kansas City were even better.

The unit gets a boost this week, too, with the return of defensive lineman Letroy Guion from his suspension. The Packers haven’t officially activated Guion, yet, but he practiced for the first time in the regular season on Wednesday.

“It’s been pretty tough watching, but at least my team was going out and taking care of business,” Guion said. “I’m just excited to get back out there with the fellas.”

Green Bay’s run defense carried the day in the victories over the Seahawks and Chiefs, holding Marshawn Lynch and Jamaal Charles to a combined 90 yards rushing on 26 attempts.

Still, it won’t hurt to have another run-stuffing big man for a 49ers ground game that features an up-and-coming back in Carlos Hyde, plus the read-option looks of QB Colin Kaepernick.

“Letroy brings a lot of experience,” defensive linemate B.J. Raji said. “He brings the energy, the awareness, the physicality.”

The Packers are aware of nothing but Sunday’s game and the challenges to get ready for it on a short week with a long flight coming up in just two days. Rodgers called it a “mental week” and emphasized making the most of their preparation time is paramount.

“We’ve beaten a lot of teams around here Monday through Saturday,” Rodgers said. “That’s how you can have a good start to the season, and we have to keep it going.”

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