His own business has been booming thanks to his return.
Sales of Lynch's Beast Mode Apparel -- which includes new gear commemorating his Seahawks comeback -- have spiked since the running back re-signed with the team Monday night. According to Mitch Grossbach, the head of operations and finance for Lynch's Beast Mode business, Beastmodeonline.com had generated around $150,000 in sales from when Lynch's return became official to midday Friday.
Grossbach estimated that December sales will end up five to seven times greater than what the website averaged in the months leading up to Lynch's return.
"Obviously, we knew a little ahead of time that there might be this possibility of Marshawn returning, so we have a team that began thinking about what can we put on sale, assuming he gets confirmed to play," Grossbach told ESPN.com. "And we designed a couple of styles."
The new gear includes hooded sweatshirts, T-shirts and long-sleeve T's that read either "Back in Action" -- which have sold out -- or "Unfinished Business." Lynch's agent, Doug Hendrickson, texted Grossbach the moment Lynch signed his deal. Grossbach then texted his team to push the new gear live.
"My phone started to blow up and I stepped out to check it," Grossbach said. "I saw that we had, within the first half an hour, we had thousands of sessions and we were selling at a rate of a couple thousand dollars in sales every few minutes. So the site had just gone crazy and spiked. I can see it exactly. This was on Dec. 23 at around 9 p.m. We had hit around $20,000 in sales within the first hour of it being announced."
Seahawks coach Pete Carroll confirmed that Lynch and Robert Turbin will play Sunday night against the San Francisco 49ers in a game that will decide the NFC West champion. But Carroll wouldn't divulge how much of a workload each newly signed running back will see or where they stand on the depth chart.
Carroll said earlier in the week that the Seahawks will "lean on" rookie sixth-round pick Travis Homer, who was their No. 4 option before Rashaad Penny went down in Week 14 and their only healthy tailback after Chris Carson and C.J. Prosise suffered season-ending injuries last week.
Turbin, who spent his first three seasons with the Seahawks, also re-signed with Seattle on Monday. Neither he nor Lynch has played since October 2018. They weren't listed on any of the team's injury reports this week, indicating full participation in all three practices.
"They fit right in," Carroll said when asked about what kind of shape they're in after their long layoffs. "You couldn't tell anything different that they weren't. The workouts before we got them here, that showed as well. So we were somewhat assured that they'd be OK and they looked really good out here."
Carroll said the coaching staff didn't try to teach the running backs the Seahawks' entire offense -- which is a somewhat different version of what Seattle ran when they were there previously -- just the game plan for Sunday night.
"They handled everything," he said. "Really, they did. You'll see the plan on how we're going to play these guys. ... I don't have any hesitation at all in what we're doing."
With the help of Hendrickson, Lynch trademarked Beast Mode as a rookie in 2007. He officially started his clothing business in late January 2015 with the launch of his website and pop-up store in Scottsdale, Arizona. The Seahawks were in the area preparing for Super Bowl XLIX when Lynch, wearing a hat with his Beast Mode logo, famously answered questions during media day with the same line: "I'm just here so I won't get fined."
According to Grossbach, they quickly sold around 2,000 of those hats.
"And then we knew we had something," he said.
Lynch recently reached a deal with Fanatics to have the online sports merchandise retailer overtake operations of Beast Mode Apparel and relaunch the company's website early next year. It's an unprecedented move for Fanatics. According to Jack Boyle, the company's president of global direct-to-consumer retail, Fanatics hasn't partnered with any other individual athlete before Lynch.
Lynch has brick-and-mortar Beast Mode stores in his hometown of Oakland and in downtown Seattle. He's reopening his store in Las Vegas in late summer or early fall of 2020. According to Grossbach, the new location will be in the shopping center at Mandalay Bay, one of the nearest on-Strip casino hotels to the Raiders' new stadium.
The new apparel commemorating Lynch's Seahawks return will be available at the Seattle store by Saturday, according to Grossbach.
"He's just the ultimate merchant when it comes to his fans," Grossbach said. "People just want a piece of him. So that's been going on for the past five years, but obviously in the past week when he announced his return, our site and our stores have just been blitzed with people looking for something to represent him with. So it's been terrific. It's really been like déjà vu from back in 2015 when he first started this."
The buzz has been felt at Seahawks headquarters as well.
"There's no question," Carroll said. "Undeniably there's an energy and juice about him being back here. He's been such an extraordinary player and character over the years. For this opportunity to come back at this time with all that's going on -- Christmas and everything, New Year's just around the corner -- it's just fitting that we were able to figure it out. I'm thrilled about the way he's brought it and learned and studied and worked at it to fit in. It's only been an addition coming in. I'm fired up for it.
"Every once in a while -- I have to tell ya -- I'm chuckling a little bit about, 'Here he is. He's back with us.' It's exciting. I like it, too, just like the fans like it."