Here's Rule No. 1 in NFL free agency -- never sign a player on the opening day.

That's when the crazy money is spent, the crazy contracts signed. The fans may love it, viewing every dollar spent as a sign of a commitment to winning by their team. But, oh, the mistakes that are made. Many of these new millionaires become salary-cap hits waiting to happen.

And the money has never been crazier than on the opening day of free agency Wednesday with the New York Giants leading the parade. New York gave defensive end Olivier Vernon a reported five-year, $85 million contract with $52.5 million guaranteed. They also gave cornerback Janoris Jenkins a five-year, $62.5 million deal with $29 million guaranteed.

I can understand the sense of urgency by the Giants. They finished last in the NFL in defense a year ago and it cost coach Tom Coughlin his job. New coach Ben McAdoo needed some defensive security and general manager Jerry Reese opened the wallet to provide it.

But neither Vernon nor Jenkins has ever been to a Pro Bowl. A pair of four-year veterans, neither has played in a postseason game. Vernon collected 71/2 sacks last season in the NFL's 25th-ranked defense and Jenkins intercepted three passes in the 23rd-ranked defense. These are not the difference-makers that their new contracts indicate they need to be.

Malik Jackson was a member of the supporting cast on the NFL's best defense last season. His Denver Broncos led the league in sacks with Von Miller and DeMarcus Ware providing a stereo pass rush. Jackson contributed five sacks to Denver's total of 52. The Jacksonville Jaguars gave him a six-year, $90 million contract with $42 million guaranteed in a bid to upgrade their 24th-ranked defense.

If Jackson is worth $90 million, what's Miller worth? The Super Bowl MVP wears a franchise tag as the Broncos negotiate his next contract.

With the abrupt retirement this week of Calvin Johnson, the Detroit Lions felt compelled to go buy a replacement in free agency and settled on Marvin Jones. They gave him a five-year deal worth $40 million with $20 million guaranteed to leave the Bengals. This for a player who did not have a 100-yard game last fall, averaged only 12.6 yards per catch and scored just four touchdowns.

The bottom line -- those who don't learn from history are doomed to repeat it.

In 2015, the Philadelphia Eagles signed cornerback Byron Maxwell away from the NFC champion Seattle Seahawks, wooing him East with a six-year, $63 million contract with $25 million of it guaranteed. Philadelphia finished 7-9 last season, 28th in the NFL in pass defense, and Maxwell has since been traded to Miami.

In 2014, the New Orleans Saints couldn't get safety Jairus Byrd's name on a contract fast enough. They gave him a six-year, $54 million contract with $26.3 million guaranteed. Byrd has started 16 games in the two seasons since and intercepted one pass. New Orleans has missed the playoffs each of those seasons and finished 31st in defense both years.

In 2013, the Dolphins lured wide receiver Mike Wallace away from the Pittsburgh Steelers with a five-year, $60 million contract with $30 million guaranteed. He spent two seasons with the Dolphins before Miami traded away his cumbersome contract to Minnesota in 2015. He failed to post a 1,000-yard season in the three years since leaving the Steelers, and the Vikings rid themselves of Wallace this week.

Those players were paid to make a difference and didn't.

You can count on two hands the players in the history of free agency who played to the level of the money and the duration of the contract. You don't find the Hall of Fame-caliber commodities like Reggie White, Deion Sanders and Drew Brees in the open market any longer.

When the rare elite player does hit free agency, as Ndamukong Suh did in 2015, the size of the contract makes it impossible for him to play to the level of the money. Suh would have to be a combination of Joe Greene and Lawrence Taylor to give the Dolphins value on the six-year, $114 million contract he signed with $60 million guaranteed.

Suh, Maxwell, Byrd and Wallace all signed on the opening day of free agency.

Yes, a team can sign a Darrelle Revis or an Aqib Talib on the opening day of free agency and go on to win a Super Bowl as the Patriots and Broncos have done. But for every Talib, there are six Maxwells, Byrds, Wallaces, DeMarco Murrays, Michael Johnsons and Dashon Goldsons.

Mistakes. Expensive mistakes. The smiles of the spenders in March become erased by the realities of December.

Wait a day. There will still be players available in free agency and they'll be more affordable. They may not be impact players -- but so few of the opening-day signees have delivered any impact. You find impact players in the draft. You find patches in free agency.

Don't overpay for them.

Listen to Rick Gosselin at 10:50 a.m. Tuesdays on Sportsradio 1310 AM/96.7 FM The Ticket with Norm Hitzges.

Twitter: @RickGosselinDMN