Brandon Marshall didn't sign with the Seahawks in order to start his 13th season in the NFL with something of a mini reunion tour; the six-time Pro-Bowl receiver signed with Seattle in large part because as he put it, "there weren't a lot of phone calls."

But it just so happened that Marshall's new team opened the 2018 season playing at Denver, the team that drafted him in 2006, and on Monday will play at Chicago, where he played from 2012-2014.

"Probably about two weeks ago I realized like, man, back-to-back, that's pretty cool," Marshall said. "The biggest one was Denver. Since I've left in 2010, I never got a chance to go back, so it's pretty cool going back. A lot of memories, so it felt good."

Of course, old memories aren't what's important right now for Marshall, especially not after he used a strong training camp to turn himself into an important piece of Seattle's offense, even at 34 years old following ankle and toe surgeries. Marshall never lost belief in his abilities, but he also was realistic enough to understand the challenges he was facing heading into the 2018 season. After playing just five games last season because of the aforementioned ankle injury—the toe surgery was for an old injury he had been playing through for years—and at an age when most players are either out of the league or on the decline, Marshall knew that plenty of teams figured he was done. That's why he was unsigned until late May, and it's why the Seahawks, while never doubting his talent, weren't exactly sure what they were getting until he was healthy.

Once Marshall got healthy and on the field in training camp, however, it became evident pretty quickly that the "old" man still had it, and in Sunday's opener he gained 46 yards on three catches, including a 20-yard touchdown.

And maybe it was a little extra excitement about playing his former team, maybe it was the emotion of making it back from those injuries and showing he can still get the job done, but whatever the reason, Marshall felt compelled to punctuate that score with what he said was the first spike of his career.

"I've just never been a big celebration guy," he said. "I celebrated one time, and it was really bad. I threw snow in the air and got fined and I was like, 'That's enough of that.' When I was in Denver I would spend like an hour every Friday with my neighbor, my brothers, and cousins trying to come up with different dances and things. After about two or three years of that, I was like this is a waste of time. Just never been a big celebration guy, so it was good to be able to check that off of my bucket list."

Marshall's return to Denver didn't go how he and the Seahawks would have liked, with the Broncos coming out on top 27-24, but despite the result, it was still a special Sunday for a player who has accomplished so much in his career, but who had to prove himself all over again this offseason.

"The thing that I always focus on is gratitude," Marshall said. "To be honest with you guys and to be honest with myself, there weren't a lot of phone calls, so to have this opportunity is amazing. Definitely the night before the game and running out of that tunnel, I just kept saying 'I'm just so thankful.' … There is something about showing people you can still do what you do. That feels good and I'm just grateful."

The Seahawks are equally grateful to have added an impact player at a stage in free agency when impact players are rarely available.

"(The acquisition of Marshall) looks great," Seahawks coach Pete Carroll said. "We're really happy about it. It took us a while to appreciate him until we were really ready to use him enough in practice and in preseason to see him go. You always could see the beautiful catching range, and he's got great savvy and understanding and all that, but we didn't know he was going to be physically OK. Once he rounded into shape and we could start to use him, he looks like a terrific asset. We're really excited about having him."

Marshall's signing looks especially important right now with Doug Baldwin dealing with a knee injury that could keep him out “a couple weeks,” according to Carroll. Marshall was going to have a big role in the offense regardless, but now he and Tyler Lockett, as well as the likes of Jaron Brown and David Moore, will be counted on even more if Baldwin has to miss any game time.

"Obviously we've all got to step up," Marshall said. "It's hard to replace Doug, you can't replace Doug. What he does, no one else in the NFL can do. I'm just going to continue to be myself. Whatever role I'm given, I'm going to take advantage of those opportunities and be grateful."

And even if a second straight game against a former team won't be Marshall's focus this week, it is a special place for him, not just because of the on-field success he had there, but also because of how his time there and the guidance of veteran teammates like Brian Urlacher helped him grow as a player and as a man and learn lessons he says "I will hold forever."

"When I first got in the league, I shot myself in the foot so many times, very volatile," he said. "I didn't understand how privileged we are, so I didn't see the big picture. So, I had to figure that out, in Miami, I figured that out. My second year going into Miami, I was like, 'Oh this is big business, I get it.' Football to me has always been life or death, where I come from, my way out. I get to Chicago, I didn't understand the business side of things. Understanding how to conduct myself as a pro every single day, leadership. There's a lot of things I learned there. When you're winning, you can do certain things, say certain things. When you're losing, sometimes you got to chill out a little bit. I never did, I just stayed the same. So, there was a lot of lessons I learned there. As far as the teammate thing, guys are watching you every single day. How do you respond to when you're injured, how do you respond to criticism, how do you respond to hard coaching?"

The Seahawks have definitely acquired a version of Marshall who has learned a lot about life in the NFL, and who has shown a willingness to pass that knowledge on to his teammates. When Marshall arrived in Seattle, Carroll noted that they wanted him to come in and focus on making the team, and wouldn't try to force him into a leadership role, but Marshall didn't wait very long to take on that role anyway. Whether it has been helping his fellow receivers or spending extra one-on-one time with rookie cornerback Tre Flowers, Marshall has been not only productive on the field, but very valuable off of it as well.

"There's a lot of wisdom there," Carroll said. "The love that is demonstrated by the older guys taking care of the younger guys is real obvious, and a real good sign… Through watching his play, you knew that he has a real wide range of stuff that he can call on. I didn't know if he would verbalize it and articulate it real well. He does beautifully. He has a willingness, too. He's real open, real easy guy to deal with in asking questions and stuff like that. So he has been great."