As the Vikings prepare for Sunday's game with San Francisco at Mall of America Field, we asked Eric Branch, the 49ers beat writer for the San Francisco Chronicle, to give us his up-close-and-personal scouting report. Here are four things you need to know … 1) The 49ers' defense has been in a groove. Which could be scary for a Vikings offense that has scored only 13 points before halftime the first two weeks. Here were Matthew Stafford's first half numbers last weekend against San Francisco: 7-for-16, 67 yards, no touchdowns, one interception. Calvin Johnson, meanwhile, had just three catches for 36 yards before the break. In Week 1, San Francisco forced Green Bay to punt six times in its first seven possessions, continuing to play with a relentless edge. The 49ers' front seven in their 3-4 defense, led by defensive tackle Justin Smith and linebacker Patrick Willis, has been both stingy and opportunistic. The Packers only managed 45 yards rushing in the opener, their longest rush a 9-yard scramble by Aaron Rodgers. Detroit averaged just 3.2 yards on its 26 rushes with Stafford delivering the long rush for 11 yards. "The defense has been incredibly successful at making teams one-dimensional," Branch said. "Eventually, they wear opponents down to where they sort of surrender and say, 'What's the point in even trying to run against this team?' And suddenly that allows the pass rush of Aldon Smith and Justin Smith and the rest to pin their ears back and get the pressure going. That creates the turnovers and the sacks that they feed off." Since the start of the 2011 season, the 49ers have forced 40 turnovers (25 interceptions, 15 fumbles). They have five sacks so far this season after registering 42 in 2011. 2) The 49ers' convincing 30-22 Week 1 win at Green Bay did wonders for the team psychologically. A year ago, San Francisco fully expected to make a playoff trip to Lambeau. But then the Packers stumbled in their postseason opener against the Giants and the 49ers hosted New York in the NFC title game. So, in some ways, the Week 1 trip to Green Bay provided a measuring stick against the only NFC team that had a better record last year. And the 49ers' decisive win was, according to Branch, "a huge confidence boost." "The feeling throughout that game was that the Niners were always entirely in control," he said. "That it happened at Lambeau Field against a team that was 15-1 last year added to the energy. I don't think the Niners necessarily lacked for confidence going into that game. But that reaffirmed for them that 'Yeah, we were pretty good last year. And we're better this year.' They didn't just win. They won convincingly, more than the final score even reflected." The defense held Aaron Rodgers and the Packers' passing attack in check for most of the afternoon. "You don't normally see Rodgers with bad body language," Branch said. "But he had body language that day, walking off the field seemingly confused by what all he was seeing. 3) Randy Moss hasn't been incredibly productive through two weeks (five catches, 61 yards, one TD). But he has fit in well. "He's been a model teammate to this point," said Branch, noting Moss' impressive football intelligence and his unwavering willingness to mentor the 49ers younger receivers, including Mario Manningham, Michael Crabtree and rookie A.J. Jenkins. Moss' playing time has been down in the first two games – which leads to the inevitable worry that he might soon get frustrated with how much he's being used. "It'll be interesting to see if he can accept being a role player," Branch said. "I do think his role will expand as the season goes on. I get the sense that the 49ers are aware that he's 35 years old and are wondering just how much juice his legs will have in January if they play him too extensively early on. So it's been calculated with the way they're managing his time." 4) Jim Harbaugh has been a significant upgrade in the head coaching position over predecessor Mike Singletary. Including the playoffs, Harbaugh has led San Francisco to 16 wins in 20 games since the start of 2011. Singletary? With many of the same players, he registered 18 wins over 40 games between 2008 and 2010. So just what exactly was Singletary's biggest shortcoming? "It was perplexing," Branch said. "As a player he was legendary and he was known for being one of the film junkies and a guy who could pick up on all these tendencies of an offense. That was a big part of what made him so great. But as a coach, he even said himself he was more of a big picture guy. And he wasn't as consumed with the details, which may have hurt. He was never really that strong with Xs and Os." So what has been Harbaugh's brilliance? Well, he's had similar priorities as Singletary, wanting the Niners to be a physical, smash-mouth running team that can wear teams out. But Harbaugh has a better feel for how to get the best out of his players "He has his players back at all times, almost to a ridiculous extent," Branch said. "He calls them his 'mighty men.' And he says they have great healing powers. He makes them into these superheroes. And he will never criticize a player even subtly through the media. It's about team and it's all handled in house. Guys want to play for him. They believe in him and they appreciate the value of his loyalty. …With Singletary, I got the impression that behind the scenes his intensity and his personality began to wear thin. And they maybe began to tune out some of the rah-rah, motivational talks they got."