Sam Bradford, Tyler Eifert head NFL's riskiest free agents of 2018

NFL fans: Let me be the first to wish you a ...

Merry Christmas!!

Free agency starts next week, as the market officially opens at 4 p.m. ET on Wednesday, March 14. For pigskin enthusiasts and NFL teams alike, it's Christmas in March.

I love it. I live for it. But in a sense, I'm also wary of it.

Don't want to curb the enthusiasm, but there will be busts in this free-agent class. It happens every year. Free agency can cultivate success (see: last season's Jaguars and Rams), but it can also induce regret (like when the Redskins gave Terrelle Pryor $8 million for ... 20 catches and one touchdown).

Here is my annual take on the riskiest free agents, Schein Nine style:

1) Sam Bradford, quarterback

In Week 1 of the 2017 season, Bradford pitched a perfect game against the Saints. Seriously, it was a genuine masterpiece, as he completed 27 of his 32 passes (84.4 percent completion rate) for 346 yards and three touchdowns. Colleague Gregg Rosenthal grades every quarterback game of the season for his weekly QB Index column, and he had Bradford's opening statement as one of the highest-rated efforts of 2017. That was the kind of outing you look for from a former Heisman Trophy winner and No. 1 overall pick. A transcendent performance.

And then his knee started barking. And he was gone.

That's Sam Bradford in a nutshell.

He's an amazing natural talent, but his availability makes him the NFL's Big Foot: You hear rumors he's a franchise quarterback, but you never see the definitive proof.

Since entering the league as the top pick in 2010, Bradford's logged 16 games in just two seasons: 2010 and '12. The guy turns 31 in November and Mike Zimmer just described his balky left knee as "degenerative." Talk about risky business ...

2) Tyler Eifert, tight end

Eifert has a long injury history, but the toughest setback definitely came at the end of his breakout 2015 campaign, when he left the Pro Bowl in a walking boot. Such a shame. The Bengals tight end scored 13 touchdowns in '15, establishing himself as a supreme red-zone weapon for Andy Dalton, who just so happened to enjoy the best season of his career. Then he suffered an ankle injury in a meaningless game, had offseason surgery and wasn't able to return to action until midway through the 2016 season.

The mismatch skills that Eifert displayed during that brief stretch of excellence remain enticing, but aberrational. After logging 15 games in his rookie season of 2013, Eifert has played in a grand total of 24 contests over the past four seasons, largely due to nagging back issues. When healthy, Eifert's hands are like catcher's mitts and he's a dreamy QB outlet -- the kind of pass catcher every NFL team wants in the toolbox. But the snake-bitten tight end's body has betrayed him.

Seemingly every preseason, there's renewed hope that this will be the season Eifert stays healthy. I'm rooting for him. But I'm not investing in him.

3) Sheldon Richardson, defensive tackle

Richardson was once a rising star. He was the NFL's Defensive Rookie of the Year in 2013 and a Pro Bowler in 2014 -- a versatile lineman with athletic traits that are nearly impossible to find in a 6-foot-3, 295-pound package.

Then he was suspended four games for violating the NFL Policy and Program for Substances of Abuse, arrested after a high-speed police chase and his production fell off a cliff.

With just 2 1/2 sacks combined over the last two seasons, Richardson's a far cry from the pass-rushing beast who appeared to be a foundational piece on Rex Ryan's Jets.

Though, still just 27 and fresh off a season where he engendered plenty of positive sound bites from Seahawks coach Pete Carroll and GM John Schneider, Richardson's sure to garner interest on the open market. Buyer beware. Hard to pay this kind of off-field (and on-field?) risk and sleep well at night.

4) Doug Martin, running back

Winston Churchill's running back: A riddle, wrapped in a mystery, inside an enigma.

As a rookie in 2012, Martin took the league by storm, racking up 1,926 scrimmage yards and 12 touchdowns. Then he disappeared for two seasons. In 2015, he was first-team All-Pro, rushing for 1,402 yards at 4.9 a pop. Then he disappeared for two seasons.

Does all of that mean he's due to re-emerge as a bell-cow back in 2018? Your guess is as good as mine.

Can he stay healthy? Can he avoid trouble? As a running back at age 29, Martin's time is running thin.

5) Case Keenum, quarterback

Was last season a mirage? The journeyman guided the Vikings to an NFC North crown, accumulating spectacular regular-season numbers (67.6 percent completion rate, 22:7 TD-to-INT ratio, 98.3 passer rating) seemingly out of thin air. Everything went right, including his interception luck. Then he turned back into a pumpkin in the playoffs: 60.2 percent completion rate, 2:3 TD-to-INT ratio, 73.5 passer rating.

Truth is, I do think Keenum can play. He has a place in this league. But some team's going to pay Keenum well over $10 million a year. Imagine writing that sentence 365 days ago. I'd be nervous.

6) Teddy Bridgewater, quarterback

Is Teddy healthy? Will he stay healthy? Can he still play? I think so? I'm Ron Burgundy?

Questions abound with the former first-round pick. The upside was there before his gruesome knee injury -- as evidenced by the Pro Bowl nod in 2015 -- but it's impossible to know the state of his game at this point. The Vikings obviously have the best idea of where he's at, and they appear content letting him walk.

Still, I could see a team signing him to start, while drafting his replacement in the first round. I predicted the Jets doing exactly this in my "QB forecaster" column earlier this week.

Bridgewater's the kind of guy everyone wants to see succeed. But it's the known unknown here that gives me pause.

7) Dominique Easley, defensive tackle

This cat is a freak -- well, in every aspect beyond his knees. Unfortunately, knees are important.

When he's right, the 26-year-old D-lineman flashes game-wrecking ability. And every team's looking for interior pressure these days. But he just missed an entire season after suffering a third ACL tear.

Someone will take a risk on the former first-round pick, given his tantalizing talent. But that someone would not be me.

8) Jordan Matthews, wide receiver

Matthews is solid, not superb. Injuries impacted Matthews' lone season in Buffalo, but he did rack up 225 catches and 19 touchdowns during his first three NFL seasons in Philly.

Under no circumstance is he a No. 1 receiver. His success at the NFL level has come in the slot. I think he's a classic, solid WR3 and should only be paid -- and banked on -- accordingly. But I'm not sure everyone's in lockstep with me here.

9) Muhammad Wilkerson, defensive end

I hope he signs with the Packers -- whom he's visiting with -- and reunites with former Jets defensive coordinator Mike Pettine. It's logical. Pettine helped Mo emerge as a stud in his first two seasons.

Wilkerson got PAID before the 2016 campaign -- and the last two years have been a debacle, marred by indifference, tardiness, benchings and awful play (see: eight total sacks since inking the deal).

I think Pettine could tap into Wilkerson's talents once again, but it's definitely no sure thing. In recent years, this is a player who's been unproductive on the field and unaccommodating off it. That's a dangerous combo.

Follow Adam Schein on Twitter @AdamSchein.

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