The Vikings opened training camp this week with eyes on a Super Bowl campaign, but the NFL is still working to see how the season will play out because of the coronavirus, and teams are trying to figure out if they will be allowed to have fans at games.

That would be a big loss for the Vikings. Since the team moved into U.S. Bank Stadium in 2016, they have posted a 23-9 record at home, a number matched only by the Eagles and Saints for the best home mark in the NFC.

The only AFC clubs with a better home-field mark in that stretch are the Patriots (26-6), Chiefs (24-8) and Ravens (24-8).

The Vikings haven't been bad on the road since 2016. Their 16-15-1 mark is 10th in the NFL and the best mark in the NFC North, with the Packers in second place at 14-18.

The Vikings have worked hard to turn U.S. Bank Stadium into one of the best home-field advantages in all of sports, with great success so far.

The club is already working under the assumption that even if fans are allowed, far fewer will be allowed in than the typical 66,000 who have attended every home game at the new stadium.

The team said in a letter to season-ticket holders that they are planning to have reduced seating in 2020, and will follow the recommendation of Gov. Tim Walz.

"We will comply with NFL rules, as well as state and federal regulations, and will approve any plans with the Governor's office," the letter read. "We can acknowledge at this time that if we are allowed to play in front of fans, games will be at a significantly reduced capacity and include a different in-stadium experience. We are planning around a number of scenarios now and will provide an update as soon as possible."

The Packers, meanwhile, have given season-ticket holders a Friday deadline to decide if they are going to opt in or out of their season-ticket plan.

Packers President and CEO Mark Murphy told the Green Bay Press Gazette that the club will allow a maximum of 12,000 fans into Lambeau Field in 2020, and that number could be decreased depending on virus statistics.

A sold-out Lambeau Field can hold over 80,000, so the Packers limiting game attendance to 12,000 should give Vikings fans an idea of how many seats the Vikings might sell — possibly fewer than 10,000 — if fans are allowed.

D-line changes

With Everson Griffen and Linval Joseph not on the roster, the Vikings defensive line was already going to look different. And now the club has learned that Michael Pierce, their big free agent defensive tackle who signed a three-year, $27 million deal in the offseason, is opting out of this season because of his family's history with asthma, putting him in a high-risk group for contracting COVID-19.

The club still will be able to field a great defensive line, but there's no doubt it's going to be harder without Pierce.

New co-defensive coordinator Andre Patterson, who has coached the defensive line since 2014, said the club will need to find other leaders in that group.

"I feel really good about the room," Patterson said. "[General Manager] Rick [Spielman] and the front office have done a great job of getting me talent. So we have great competition in that room from top to bottom.

"Obviously I'm excited about Ifeadi [Odenigbo] to continue to improve as a player. He made great strides last year and he is a tremendous hard worker. I think he's busting his tail right now to continue to improve. I had to talk to him about not overtraining and not working too hard. I think the leadership part of it just comes natural. You can't make anybody be a leader. It just comes natural.

"So whoever is in that room that's going to be that guy to step forward and take that role, it will happen naturally. Just because somebody has played here for a number of years and been a good player for a number of years, you don't want that person to do something that makes them uncomfortable. You want them to continue to be themselves and do what they have done to help them be successful. The worst thing they can do is change that. I think we're going to be in good shape and I really like the makeup of the D-linemen."

Twins talk travel

Baseball got a big scare this week when the Marlins had several players test positive for the coronavirus and MLB had to postpone their games through Sunday. Every pro sports league is doing its best to keep team members safe and healthy.

Twins President Dave St. Peter explained how the club is handling travel plans this season.

"We'll travel with a few more players because the rosters have been expanded and that's part of it," St. Peter said. "With that will come a couple of additional staff members, trainers and such. But for the most part, we're trying to limit our traveling party as much as we can, just to help and ensure the safety of our club and that remains obviously our top priority. No major changes.

"One thing I would point out about travel is the regional nature of our travel. Thankfully where we play [in the AL Central], we have about as good of travel as any team in the game with just trips to Chicago and Cleveland, Detroit, Kansas City, Pittsburgh, Cincinnati, along with Milwaukee. We feel very fortunate."

The Marlins are the only club that has had players test positive since the start of the regular season so far, but every club will be on high alert all season.

Jottings

• Vikings co-defensive coordinator Adam Zimmer on his expectations for second-year cornerback Kris Boyd, who could be a big surprise this season: "I like Kris a lot. I think he has a good mental attitude and he works really hard at it, you can give him one thing to do and he will work at it nonstop. He did that at the end of the year and he played great on special teams for us. I know he's just going to hone in some little details of the position and keep improving his technique. But I like his mental makeup. I think he's a competitor and he wants to be great. He's going to do everything he can to be in the mix for us."

• A lot of geniuses were upset when the Twins didn't want to pay Craig Kimbrel a ton of money to be their closer last season. Instead Kimbrel signed a three-year, $43 million deal with the Cubs. After a tough first outing this season, allowing two runs while recording one out against the Reds on Monday night, Kimbrel has allowed 17 runs over 21 innings in two seasons with Chicago.

Sid Hartman can be heard on WCCO AM-830 at 8:40 a.m. Monday and Friday, 2 p.m. Friday and 10 a.m. Sunday. • shartman@startribune.com