The 49ers fired the battle's first shot with their trade for wide receiver Anquan Boldin, but it's the Seahawks who have done the most to improve their team this offseason.
In fact, the Seahawks did more than any team in the entire National Football League.
That isn't meant to knock the moves made by the reigning NFC West champions. The 49ers made a few shrewd free agent signings this spring, and then followed that up with an excellent showing in the 2013 NFL draft.
However, the 49ers also didn't have many holes to fill, so a measured approach suited them well. The Seahawks, on the other hand, had some catching up to do if they hope to unseat San Francisco in the division.
So they blasted away like Timothy Olyphant's character in an episode of Justified.
First, general manager John Schneider added to Seattle's offensive firepower with a dynamic playmaker in wide receiver Percy Harvin, who the team acquired in a trade from the Minnesota Vikings before signing the 24-year-old to a six-year, $67 million contract.
The Seahawks paid a hefty price, dealing a package of picks that included this year's first-rounder. However, the odds of Seattle getting a game-breaker of Harvin's quality with the 25th overall pick were slim to none, and Harvin adds an entirely new dimension to the Seahawks' read-option offense.
The Seahawks were just getting started.
The team then took major steps to address a mediocre pass rush that may be without 2012 sack leader Chris Clemons to begin the 2013 campaign. Within days of each other, the team signed Detroit Lions defensive end Cliff Avril and Michael Bennett of the Tampa Bay Buccaneers to reasonably priced contracts.
The pair combined for 18.5 sacks in 2012, and not only does their addition compensate for Clemons' ACL injury and the free-agent defection of defensive tackle Jason Jones, but it also provides the Seahawks with a great deal of flexibility on the defensive line.
But wait, there's more!
The Seahawks then added yet another ex-member of the Minnesota Vikings, inking free agent cornerback Antoine Winfield to a one-year deal.
Granted, at 35 years old Winfield isn't the player he once was. However, Winfield tallied over 100 tackles in 2012 and was the top-rated cornerback in the entire National Football League a season ago according to Pro Football Focus.
In Winfield and Richard Sherman, the Seahawks now have PFF's top two cornerbacks from a season ago. Throw in cornerback Brandon Browner and safeties Earl Thomas and Kam Chancellor, and Seattle may well now have the best secondary in the NFL.
The team carried that positive momentum right into last week's NFL draft.
Even without a first-round pick, the Seahawks were still able to have a very successful draft. The team added additional depth on the defensive front with tackles Jordan Hill of Penn State and Jesse Williams of Alabama. On the draft's third day they picked up small-school star Ty Powell, who could blossom into at least a solid reserve at the hybrid "Leo" position.
Seattle didn't ignore the offense either. In second-round pick Christine Michael, the Seahawks gained a talented running back who can back up and perhaps one day replace Marshawn Lynch. Kansas State wide receiver Chris Harper gives quarterback Russell Wilson yet another weapon in the passing game.
Which NFL Team had the best offseason?
Bleacher Report NFL National Lead Writer Ty Schalter is a fan of what the Seahawks did in the draft, grading Seattle's haul a "B+" and writing that "If we count Harvin, this could be an A-, but as it stands, the Seahawks just got a lot of good players at decent value."
It's worth noting that, as good as these moves look on paper, they don't necessarily mean anything. There are still 16 games to be played, and there are plenty of other contenders who had successful offseasons, from the aforementioned 49ers to the Baltimore Ravens and Atlanta Falcons.
With that said though, you're going to read and hear plenty of stories over the next few months that mention the Seattle Seahawks and the Super Bowl in the same sentence.
That's what happens when an 11-win team absolutely kills it in the offseason.
You know, like the Seattle Seahawks just did.