NFL free agency is a smart way for teams to complement their draft picks while building contending rosters.

If done right.

Free agency can be a minefield, as a wrong move can cause more harm than good, both financially and otherwise. Plenty of examples exist from an offseason ago, including Le'Veon Bell's four-year, $52.5 million contract with the New York Jets and Nick Foles' four-year, $88 million deal with the Jacksonville Jaguars.

This offseason, there are more "buyer beware" tags. Factors like age, production compared to alternatives and injury history, among others, make the following players risky pickups on the open market.

Tyler Eifert, TE

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Tyler Eifert played a full 16 games for the Cincinnati Bengals in 2019, but that serving as an argument in his favor should be a red flag. It was the first time the tight end played in more than eight games in a season since 2015 and only the third time he managed double-digit appearances.

The reality? Eifert played less than 50 percent of his team's offensive snaps, tallying 43 receptions for 436 yards and three scores. He'll be 30 years old next September.

Teams could buy into the idea that Eifert has upside as a top tight end after he showed he can stay healthy. But when you look closer, it's clear he was on a snap count, and 2019 might've been his ceiling.

Philip Rivers, QB

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Philip Rivers wants to keep playing in 2020, though it might not be with the Los Angeles Chargers.

And the Chargers would at least be somewhat justified in letting him slip away if there's a bidding war. Rivers completed 66 percent of his passes for 4,615 yards in 2019 but heavily regressed in touchdowns (23 to the previous season's 32) and threw eight more picks (20). His touchdown percentage, adjusted yards per attempt and quarterback rating all went down.

Keep in mind Rivers is 38 years old, and he's never played for another franchise. If he has to adjust to a new system and has growing pains, acquiring him could backfire tremendously.

The aforementioned warning signs probably won't stop some team from opening up the checkbook if Rivers is done with the Chargers. But like with Foles last year, the result could be negative.

Andrew Whitworth, OT

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Andrew Whitworth is a big name who could return to the Los Angeles Rams instead of joining his third team since entering the league in 2006.

Whitworth, 38, had regression issues last year, receiving more help than any other left tackle in football and seeing his Pro Football Focus grade dip to 72.8, down from 83.1.

This situation calls to mind the Trent Brown saga. The Oakland Raiders overpaid the limited starter last offseason (four years, $66 million), and he hovered around the same ho-hum play while struggling with injuries. The overarching theme is a thirst for left tackles at the NFL level.

In short, teams aren't letting the best offensive tackles hit the market, and the fact that the Rams haven't locked up Whitworth prior to this hints they might be comfortable with him slipping to free agency.

A.J. Green, WR

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The warning signs are there for A.J. Green, yet it likely won't stop teams from throwing money at a wideout with nearly 9,000 receiving yards and 63 touchdowns over 111 games.

Front offices might give him the benefit of the doubt after he produced like he did on a squad like Cincinnati, even though he missed all of 2019 while his team went 2-14 and secured the top pick in the 2020 draft.

But there are red flags. Green also missed significant chunks of time in 2016 and 2018, and he will turn 32 in July. There's no doubt he was once a game-altering player who could prop up a middling starter or help develop a rookie passer.

Some team will pay up, though the results might not be ideal.

Ndamukong Suh, DL

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Is another team going to make the mistake of buying into Ndamukong Suh?

The Tampa Bay Buccaneers did last offseason after losing Gerald McCoy, and they only got 2.5 sacks in 16 games from the formerly elite interior presence.

At Pro Football Focus, Suh's grade was 69.7 (down from 80.2 in 2018), so it wasn't as if he was doing much else. While playing 77 percent of the defensive snaps, he put up just 10 hurries and 24 pressures.

Maybe this wouldn't have been so bad if the Buccaneers hadn't doled out $9.3 million for one year. But another team can't afford to make a similar mistake, not after Suh's regression. There's also the fact that he is now 33 years old.

Melvin Gordon III, RB

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Le'Veon Bell got a nod in the intro for a reason (789 yards and three scores on 3.2 yards per carry), and Melvin Gordon III could be the latest example of a team regretting a contract. For another regret, just ask the Los Angeles Rams about Todd Gurley II and his record-breaking deal.

The Chargers at least seem to be on the right path after not giving in to Gordon's holdout. The 26-year-old running back returned to the team at the end of September and ended with 612 yards and eight touchdowns while averaging 3.8 yards per carry.

Gordon scores lots of touchdowns (36 in 67 career games), but he averages just four yards per carry. His usage in the passing game is something teams otherwise replace with committee looks if they haven't found an all-around back of their own, and those are in increasingly bountiful supply. It's an unspectacular resume, especially considering he was a 2015 first-round pick, and it's clear he's been angling for a top-flight contract.

The team that bites could be the next to experience immediate regret.