Nnamdi Asomugha of the Philadelphia Eagles walks off of the...

Nnamdi Asomugha of the Philadelphia Eagles walks off of the field after losing to the New England Patriots, 38-20. (Nov. 27, 2011) Credit: Getty Images

There may be no better example of the promise -- and the perils -- of NFL free agency than what happened during the signing frenzy after last year's lockout was lifted.

Once the league and the NFL Players Association agreed to end their dispute in late July, the Eagles went on a free-agency spending spree that made them the early favorites to win the Super Bowl. The Giants essentially sat on their hands and invited plenty of criticism for their inactivity. Especially after an early-season spate of injuries.

But in the end, it was the Giants, not the talent-laden Eagles, who hoisted the Vince Lombardi Trophy last month at Lucas Oil Stadium in Indianapolis.

The Eagles? Despite signing coveted free agents Nnamdi Asomugha, Cullen Jenkins, Jason Babin, Ronnie Brown and Vince Young, they didn't even make the playoffs.

The lesson here: Free agency is nice, but drafting well and filling holes when necessary on the open market is the better way to go.

So as the free-agency signing period opens Tuesday, when NFL teams can start bidding on many of the league's most talented players, the two words that teams would be smart to remember are "buyer beware.''

Not that there's anything wrong with making shrewd investments on a free agent here or there. But if there's one thing we've learned since unrestricted free agency came to the NFL in 1993, it's that you can't buy a championship. The Eagles found that out last year, just as the Redskins did several times before that. And don't forget the Jets teams in the early years of free agency; they'd be winners in March, but not December.

"We pride ourselves in trying to have enough depth at every position," said Giants general manager Jerry Reese, who signed a punter (Steve Weatherford) and a center (David Baas) in free agency last year. "Next guy up, and our coaches do a terrific job when the next guy up, whatever his skill set is, they do a good job of implementing him into the offense. Injuries are what they are, but we never use that as an excuse."

The Eagles now hope the free-agent signings from a year ago will pay off down the road, especially after having a full offseason to become more acclimated to the coaches and the revamped roster.

"It's exciting to have those guys, have them for an offseason," general manager Howie Roseman said. "We knew that it wasn't just a move for 2011, it was a move for the future of the Philadelphia Eagles, and we're excited about what they're going to bring, having some experience in our system, being in our atmosphere, and I think the sky's the limit for the guys that we brought in last year."

They can only hope. In an era in which it's awfully tempting to spend big on the open market for players who have proved themselves, it takes patience and belief in the players you develop in the draft to really build championship teams in this league. The Giants are the ultimate example of that theory.

Sure, they've been reasonably active in free agency in certain spots -- they brought in defensive tackle Chris Canty, linebacker Michael Boley and safety Antrel Rolle as free agents -- but the core of their team has been together for their two Super Bowl wins in the last five seasons.

That includes quarterback Eli Manning, defensive end Justin Tuck, linebacker Mathias Kiwanuka, running backs Ahmad Bradshaw and Brandon Jacobs (who was just released) and offensive linemen David Diehl, Kareem McKenzie and Chris Snee.

Add in recently drafted players such as defensive end Jason Pierre-Paul, wide receiver Hakeem Nicks and cornerback Aaron Ross, not to mention undrafted receiver Victor Cruz, and there's the formula for success.

Opening up the checkbook in free agency may be all well and good. But in this league, it's not what will get you to where you want to go.