San Francisco 49ers

5 things to watch, 49ers vs. Lions: Will Pettis thrive in Goodwin’s absence?

Here are five things that could decide the outcome of the home opener Sunday when the 49ers host the Detroit Lions.

Dealing with injuries

The 49ers will be without receiver Marquise Goodwin, who left last the loss last week in Minnesota with a deep thigh bruise. The speedster didn’t practice this week, indicating San Francisco might have to call on rookie Dante Pettis to provide the downfield element to Kyle Shanahan’s passing attack.

Pettis had a strong debut filling in for Goodwin against the Vikings, catching two passes for 61 yards, including an impressive 22-yard touchdown that kept the 49ers in the game. Goodwin’s absence will also lead to activating rookie seventh-round pick Richie James, who led the team in receiving during the preseason. James could give San Francisco a dynamic in the passing game the Lions are unprepared for after being inactive last week.

At linebacker, veteran Malcolm Smith (hamstring) returned to the field in Friday’s practice, but is questionable for Sunday. If he can’t go, Elijah Lee would be the favorite to start opposite promising rookie Fred Warner. Brock Coyle was placed on injured reserve this week after suffering a concussion and T4 compression fracture in his vertebra. The team signed former Seahawk Terence Garvin, who is an option both at “Sam” linebacker and inside.

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Linebacker is the team’s thinnest position this week. Fortunately for the 49ers, Reuben Foster is eligible to return from suspension Week 3 against the Chiefs.

It looks as if undrafted rookie Najee Toran will start at right guard. Toran is the de facto fourth option at the position with Mike Person (foot), Joshua Garnett (dislocated toe) and Erik Magnuson (hamstring) injured. Magnuson returned to practice this week after straining his hamstring in Week 2 of the preseason. He said it was a six-to-eight week injury. Saturday would mark four weeks exactly. He’s listed as questionable.

Red-zone woes

The 49ers aren’t overhauling their red-zone plans for Sunday after going 1 of 4 in Minnesota. They believe their issues have more to do with execution than game planning. They shot themselves in the foot with mistakes, not play design, including a fumble at the 1-yard line, a missed throw from Jimmy Garoppolo to an open George Kittle, and Pierre Garçon dropping a catchable pass in traffic.

“I think if we make all three of those, which we’re very more than capable of making the higher percentage of the time than not, then we had a great day in the red zone,” Shanahan said. “That’s the entire NFL. It gets tougher down there, and when you have an opportunity and you miss it you will not have a good day in the red zone. (We’re) not going to reinvent the wheel, but we’re going to try and get better at that stuff.”

Playing in a friendly environment at Levi’s Stadium should help. So should going against a Lions defense that allowed 349 yards of offense and rookie Sam Darnold to average 9.4 yards per passing attempt in his first career start.

Forcing turnovers

Lions quarterback Matthew Stafford was intercepted four times during the Monday night loss to the Jets Week 1. The 49ers, of course, lost the turnover battle in Minnesota last week, 4-1. Much like the offense, San Francisco’s defense failed to take advantage of potential game-changing opportunities, which included dropped interceptions from safety Jaquiski Tartt and Warner.

The 49ers will have a better chance at forcing turnovers with an effective pass rush. DeForest Buckner spearheaded that effort last week, making 2 1/2 sacks, nearly matching his three-sack total from 2017. How his supporting cast is used bears watching. Last year’s No. 3 overall draft pick Solomon Thomas played just under half the defensive snaps while Arik Armstead led the defensive line with 59.

“(Armstead) is playing with a mindset and if he continues with this in the way he’s going, he’s a very large human being,” defensive coordinator Robert Saleh said this week, “and when he plays like a very large human being and plays with that mindset of power, he is a very, very hard human being to block. Very hard. When you’ve got two 6-foot-7 trees in the middle pushing the pocket and playing with that mindset, it is very hard for a quarterback to be able to see down the middle of a field.”

Piecing together the running back corps

Last week didn’t offer much clarity as to how the 49ers are going to use their running backs without Jerick McKinnon. Alfred Morris and Matt Breida received 12 and 11 carries, respectively, and Breida was the only back targeted in the passing game. He was thrown at twice and made one catch for five yards. Morris was responsible for the biggest gaff in the game, when he fumbled at the 1-yard line, taking away a chance for San Francisco to tie the score at 10-10 in the first half.

McKinnon was expected to be used frequently in the passing game thanks to his ability to line up all over the field and create mismatches. The 49ers are clearly lacking that option, which means they’ll be easier to defend with blitzes.

“It’s a matchup league and everything is about matchups,” Shanahan said. “So, you always look at how your receivers can be corners and how your tight ends and backs can beat safeties and linebackers. Those are your options. When you have a tight end or a running back who can beat almost any linebacker or any safety, it takes a lot of pressure off of people. That’s how McKinnon is.”

That was clearly a problem last week against the Vikings, who took advantage of San Francisco’s injuries along the right side of the offensive line, forcing Garoppolo to make quick decisions without his top outlet in McKinnon. Expect the Lions to try blitzing Garoppolo heavily to see if they can replicate Minnesota’s success. And expect the 49ers to have a better plan for Garoppolo to get rid of the ball quickly.

How will Garoppolo bounce back?

San Francisco’s franchise quarterback is in foreign waters this week. He’s preparing to rebound from a loss for the first time in his career after beginning 7-0. The three-interception performance in Minnesota, naturally, led to headlines and sports-radio fodder suggesting Garoppolo’s 5-0 finish to 2017 was an aberration, not a sign of potential stardom.

Garoppolo made bad throws in key situations, to be sure. But he also kept San Francisco in a game where it likely would have been blown out in previous seasons. Losing by eight points after falling behind 24-6 to a contender, with a defense that ranked No. 1 in yardage and scoring last season, is a silver lining to Garoppolo’s first defeat.

“There’s going to be games when sometimes it’s not perfect,” left tackle Joe Staley said. “But there’s going to be games where he has five touchdowns, no interceptions and throws for a s--- ton of yards. We have all the confidence in the world in Jimmy. He’s a great quarterback.”

But silver linings don’t mean much, if anything, week to week in the NFL. If Garoppolo doesn’t put up a strong performance in his first home start since signing his massive $137.5 million contract, against a heavy underdog, the questions about future stardom with persist.