Gone was his running mate of the past four seasons. The Vikings' blockbuster trade that sent Stefon Diggs to the Buffalo Bills in March broke up one of the NFL's top receiving duos and eliminated the yin from Thielen's yang.
But there was little doubt around the Vikings' organization about the path Thielen could blaze as a true No. 1 receiver.
Thielen, who went from undrafted free agent on a college tryout to two-time Pro Bowler, became the unquestioned veteran leader of the position group. As the elder statesman amid 20-somethings, Thielen, 30, assumed the responsibility of bringing along a crop of promising yet inexperienced receivers, including the player Minnesota drafted to replace Diggs: Justin Jefferson.
"We talked, really before everything shut down, and I said to him, 'Hey, I want you to lead this group. This is your group to lead, and the better off that everybody is around you, the more success you can have,'" Vikings wide receivers coach Andrew Janocko said. "And he understands that as a collective the better we can be as a group the better success he'll have."
Fighting back from an injury-riddled 2019, Thielen tried to set an example for his young teammates, and it has paid off. Between Thielen and Jefferson, the Vikings have the two highest-graded receivers in the NFL, according to Pro Football Focus, and the duo has played a major role in this offense finding its groove heading into Sunday night's game at the Seattle Seahawks (8:20 p.m. ET, NBC). The two receivers and running back Dalvin Cook have combined for 70% of the Vikings' yards from scrimmage.
As Thielen leads the receivers through a period of transition, a new dynamic duo is forming in Minnesota.
Nine years stand between Thielen and Jefferson.
Sometimes it's obvious, like when Thielen broke out his rendition of "The Griddy" on the sideline in Houston on Sunday, the touchdown dance Jefferson made famous during his record-setting season at LSU that led to him being drafted in the first round. That drew a good laugh out of Jefferson and further endeared him to his veteran teammate.
"It’s funny because of the fact that I’m the youngest player in the whole locker room," said Jefferson, 21. "I hear it a lot, especially from our guys. It’s just connecting with them through football. I mean, outside of here, they have their own families, people have other things to do. Me, I’m single, don’t have any wife or any children. So I’m just kind of sitting at home by myself doing my own things. Just connecting with them through football, trying to talk with them whenever I can, really."
Thielen joked that he has been trying to avoid being "the old guy in the room" and certainly doesn't feel his age. But being able to pass off his experiences from seven years in the NFL and the life lessons he has learned becoming a husband and father have given him an appreciation for the role.
"It helps me stay young," Thielen said. "Being around these guys and learning these things that they like to do and just how things change the younger you are. I think it's been a really cool dynamic to be able to [share] some life lessons as well. So much of the talk is about football and what we do on the football field, but I think it's so important when we're together 24-7 that you're able to [share] life lessons and things like that and not only learn from your mistakes on the football field but mistakes that I've made in my life that I can share with these guys and try to help them not make those same mistakes."
The Vikings stuck Thielen with Jefferson at the start of training camp. Most days during individuals, they worked one-on-one on a side field. With the next most experienced wideout being Tajae Sharpe, a free-agent acquisition who spent 2016-19 in Tennessee, Thielen took a hands-on approach as a mentor to more of the group than just Jefferson.
"Adam is a natural teacher," rookie receiver K.J. Osborn said. "So for me, I'm a visual learner, so being out there and being able to watch him work, the type of routes that he runs, why he's running it, I'm able to come back and talk to him -- why he did this, why he did that -- and Adam is great with it."
Thielen's willingness to teach and coach is a skill he has honed watching receivers come and go during his time in Minnesota. His approachability is the glue that keeps the receivers room together.
"He's the complete opposite of aloof," Vikings quarterback Kirk Cousins said. "If he was aloof and distant -- whatever the opposite of that is -- that's how he is with the younger players and guys on the team. Very open and helpful. One of the best ways to lead is through your production on the field, and he's doing that. But he certainly does as well with his attitude and his personality, which I think has a positive impact not only on the young receivers, but our offense and our locker room."
It takes a village to break in a first-round talent. Just ask Vikings offensive coordinator Gary Kubiak.
"Because not only are you coaching him every day and trying to get him ready to go, but you go to your veteran players and say, 'OK, now listen. When we do this, he needs some help here. He's struggling with this during the week, make sure he's right.' Or I may call a play and I may say ‘Hey Kirk, make sure you hit [Jefferson], remind him of this or that,'" Kubiak said. "So I think we're all conscious of that, but we also understand how much he can help us be successful and help this team win. So we've got to all be committed to that."
Thielen leads the NFL with catches on 49.06% of his team's targeted air yards. He had 110 yards and two touchdowns in Minnesota's season-opening loss to the Green Bay Packers and another monster day in Houston, catching eight passes for 114 yards and a touchdown.
Since Jefferson's seven-reception, 175-yard, one-touchdown performance against Tennessee in Week 3, he has continued to grab the attention of teams around the league as the most promising rookie receiver in his draft class.
There's no one happier for his running mate than Thielen, the teacher who might have learned a thing or two from his student.
"There's things that I've seen him do in training camp and then in these first few games that I've definitely tried to apply to my game," Thielen said of Jefferson. "Just the way that he runs routes, his shiftiness and what he does at the top of his routes has been fun to watch. I've tried to apply some of those things to my game."
For Jefferson, studying Thielen is teaching him how to be a pro.
"I watch Adam, especially in practices, trying to learn everything that I can on how to run different routes or what do you do at the top of routes if the DB is playing this type of way," Jefferson said. "Adam has a lot of years under his belt in the NFL, and I’m just trying to learn everything I can from him. He’s giving me reliable information and he’s helping me every step of the way."
The Vikings have found what works in this offense when they have a No. 1 and 2 receiving threat. They've made important strides as they try to rebound from an 0-3 start. And it started with Thielen's leadership.
"They all listen to him," coach Mike Zimmer said. "I think Justin is a guy who wants to take everything, and I've been told that [Adam] loves how Justin goes about his games, goes about the way he works, the way he goes out to practice and continually tries to get better. I think that's a credit to Adam, as well."