The Lions and Vikings head into Sunday's game at TCF Bank Stadium scratching their helmets in disbelief over what happened in Week 1. The Lions blew a 21-3 lead in San Diego, giving up 404 yards passing in a 33-28 loss. As for the Vikings, about the only thing they did well was guess the coin toss. It was pretty much all downhill from their en route to a 20-3 loss at San Francisco.

How will each team respond Sunday? Are the Lions a shell of themselves defensively after losing leader and tone-setter Ndamukong Suh? Will Calvin Johnson be targeted more than four times and be more of a factor than he was in Week 1 (two catches, 39 yards)?

For some answers, we turned to Tim Twentyman, lead writer and insider for DetroitLions.com and former Detroit News beat writer.

MC: How much of Sunday's defensive collapse and league-worst 483 yards allowed is the end result of losing Ndamukong Suh to free agency, and what are the other defensive changes that have weakened this unit from last season, assuming of course that you think it is weaker?

TT: This defense is weaker. You don't lose the most dominant defensive tackle in the game and expect there won't to be an impact. That being said, I'm not sure how much Suh would have helped the Lions last week in San Diego. Philip Rivers picked the defense apart with a barrage of short passes and screens, 32 of his 42 passing attempts were under 10 yards. The problem the Lions defense had was rallying to the football, taking poor angles and tackling. Defensive coordinator Teryl Austin believes those issues are correctable. We'll see if he's right on Sunday. The Lions played that game in San Diego without their current best player on defense – linebacker DeAndre Levy. He's their best cover linebacker and an instinctive player in the run game. He's dealing with a hip injury and has missed practice all week so far. His status for Sunday is yet to be determined. Haloti Ngata played well in place of Suh, but they're different players. Ngata's game is predicated more on occupying space and blockers and allowing others to make plays around him. The defense is also trying to replace the six sacks DE George Johnson gave them last year (2.5 in two games vs. Minnesota). He left in free agency. The defense returns nine starters from the second-ranked unit from a year ago, but without Suh they are a little weaker. Without Suh and Levy they're a lot weaker.

MC: What happened to the Lions after they went ahead 21-3 on Sunday and what area do you think they're most vulnerable when they play the Vikings?

TT: They couldn't stay on the field on offense and couldn't get off of it on defense. The Lions were one of the best third-down defenses in the NFL last year, but San Diego converted over 50 percent on the money down in Week 1. To make matters worse, the offense was just 3-of-10 on third down. Most of those issues on third down on both sides of the ball came in the second half and helped the Chargers fight their way back into the game and eventual take the lead. The Lions ran just 47 plays on offense and had just 40 up until the last two-minute scoring drive. Where are the LIons vulnerable against the Vikings? The defense has to prove they can stop Minnesota's short and intermediate passing game. They were vulnerable in that area vs. the Chargers. The Vikings have no-doubt seen the film and could look to attack them in a similar fashion.

MC: A year ago, the Lions had 12 sacks and five interceptions in two wins over Teddy Bridgewater. Do they have the personnel to keep creating that much stress on a young quarterback?

TT: Teryl Austin and that defense can still bring the heat; they're just doing it in a few different ways than NFC North opponents might be used to. This was a team that relied on their front four to provide the pressure for a long time. That gave them the freedom to drop seven or being creative with their run fits. They've typically been one of the least blitzing defenses in the NFL the past few years. That appears to be changing this season. The Lions are utilizing their linebackers as pass rushers much more than they have in the past. Part of it is to combat the losses of Suh, Johnson, Nick Fairley and others, but it can also leave an offense guessing as to where the rush is coming from. DE Ziggy Ansah recorded three sacks against the Vikings last year. He's still manning that right edge and he's off to a good start in 2015 with one last week. The Lions have also added a speed element to their edge rush in the undersized DE Phillip Hunt. He also recorded a sack last week. They still have the personnel to make things rough on Bridgewater, they'll just unleash them in a little different manner than the Vikings might be used to seeing.

MC: Calvin Johnson had a quiet game. Why is that and do you expect him to be a bigger part of the game plan against the Vikings?

TT: The same questions that were being asked this week in Minnesota in reference to Adrian Peterson's lack of carries were being asked here in Detroit about the lack of targets for Calvin Johnson. I asked on Johnson Wednesday if there should ever be a situation where he gets only four targets in a game that he's healthy for. He just laughed and said that was my answer. The Lions ran only 47 plays, which was part of the problem, but the Chargers did a good job of always keeping a safety over the top on Johnson. He even saw some triple teams from time-to-time. Offensive coordinator Joe Lombardi said the four targets Johnson got last week was "an anomaly" and he fully expects Megatron to get his targets in the week's to come. I expect the Lions to move Johnson around this week and put him in motion more to free him up. He wasn't too happy about losing a game in which he had just four targets. Expect much more of Megatron on Sunday.

MC: How is Matthew Stafford's arm injury and where do you stand on the debate as to whether Jim Caldwell and Joe Lombardi are good for Stafford's overall effectiveness or too stifling for a gunslinger with a big arm and a Megatron at receiver?

TT: Stafford's arm is fine. He took a big hit from LB Melvin Ingram and lost some feeling in it for a bit last week. He's been wearing a sleeve over it this week, but he's practiced fully all week and says he's ready to go. Caldwell and Lombardi have made it very clear that limiting Stafford's interceptions and increasing his completion percentage have been major goals since the first day they both got here. They've reined him in a bit, hoping to play more of a complementary brand of football. It was successful last year as the Lions had one of the best defenses in the league, ranked in the top 10 in turnover ratio and won 11 games and made the playoffs. Stafford was also a Pro Bowler (alternate) for the first time in his career. Now in the second year of Lombardi's system, Stafford has more freedom to push the ball down the field, but he'll never have a green light under this regime to throw into some of the triple and quadruple coverages he got away with in the past when he was zeroed in on Johnson and only Johnson. The goal is to make Stafford a more complete quarterback and an overall more effective quarterback by allowing him to use all the weapons he has at his disposal. There are some fans here in Detroit who miss the gunslinger, but Caldwell is trying to build a complementary football team that doesn't turn the football over. No room for reckless gunslingers in those plans.