The NFL Draft is the life blood of every NFL team. Roster acquisitions in free agency and through trades can help a team go from pretender to playoff contender or extend a championship window. Teams should have a sense of whether veteran players acquired via trade and in free agency (newcomers and re-signings) are paying off as expected by the time the NFL season is at the quarter mark.

Players obtained in these manners have been examined to determine the best veteran acquisition for each NFL team. Players receiving franchise tags weren't considered because they didn't have a legitimate chance of switching teams like restricted and unrestricted free agents that opted to re-sign with their own clubs.

The additions for each team are listed from worst to best. Productivity and cost are major considerations in the rankings. Each player's contract is in parentheses to help put the rankings in financial context.

William Gay, CB ($7.5 Million/3 Years)

Upgrading the secondary was an offseason priority for the Steelers, who took cornerbacks in the first and second rounds of this year's draft. But the 10-year veteran is still Pittsburgh's best defensive back despite the new additions.

Doug Martin, RB ($35.75 Million/5 Years & worth up to $42,937,500 with salary escalators and incentives)

Tampa Bay's running game has really sputtered ever since Martin, who was second in the NFL last season with 1,402 rushing yards, went down with a hamstring injury in the second game of the season. The offense has become too one dimensional with second-year quarterback Jameis Winston shouldering too much of the load.

Jeremy Kerley, WR ($850,000/1 Year with additional $350,000 in incentives)

Bruce Ellington's season-ending hamstring tear late in the preseason prompted the 49ers to acquire Kerley from the Detroit Lions at roster cut downs for offensive guard Brandon Thomas. Kerley is the 49ers' leading receiver with 18 catches for 202 yards with one touchdown.

Charles Johnson, DE ($3 Million/1 Year)

Carolina let Johnson become a free agent in early March instead of keeping him on the books this year with an $11 million salary and $15.02 million salary cap number. He quickly returned at a bargain basement price. The Panthers are getting a good value with Johnson considering Mario Williams got a 2-year, $17 million deal (worth up to $20 million with incentives) from the Miami Dolphins after the Buffalo Bills let him go because of a disappointing 2015 campaign.

Vincent Rey, OLB ($10.5 Million/3 Years & worth a maximum of $11.5 million with salary escalators)

Rey has been Cincinnati's most consistent linebacker this season. Expect Rey's playing time to decrease since Vontaze Burfict has returned from a three-game suspension for repeated violations of player-safety rules.

Case Keenum, QB ($3.635 Million/1 Year)

Keenum may not be convincing other NFL teams that he is a legitimate starting quarterback. However, the Rams probably wouldn't be 3-1 if first overall pick Jared Goff was playing quarterback instead.

Yes, Case Keenum is the Rams' best veteran acquisition. Getty Images

Russell Okung, OT ($5 Million/1 Year with an additional $3 million in incentives)

Okung has helped solidify Denver's revamped offensive line. It remains to be seen whether the Broncos will pick up the option on Okung's contract for an additional four years worth $48 million between the end of the season and the start of free agency on next March 9.

Nigel Bradham, OLB ($7 Million/2 Years with a $500,000 2017 base salary escalator)

Bradham has been impressive in his reunion with defensive coordinator Jim Schwartz, who had the same position with the Buffalo Bills in 2014. Off-field issues are the main thing that have tripped Bradham up since signing with the Eagles in March.

Matt Forte, RB ($12 Million/3 Years & worth a maximum of $16 million through salary escalators)

The 30-year-old still has some gas left in the tank despite entering the season with over 2,500 career touches (combined rushing attempts and receptions). Forte is 13th in the NFL with 371 yards from scrimmage.

Derrick Johnson, ILB ($21 Million/3 Years)

There was some speculation after the 2015 season that the Chiefs might look for a younger veteran instead of re-signing the 33-year-old linebacker. Johnson has been a stabilizing presence for a linebacking unit bit by the injury bug.

Mo Claiborne, CB ($3 Million/1 Year plus $750,000 in incentives)

Claiborne returned to the Cowboys after the team declined to pick up a fifth-year option for this season in 2015, which would have paid him $11.082 million. He is finally starting to play like the Cowboys hoped he would when they traded up to select him with the sixth overall pick in the 2012 draft.

Brian Hoyer, QB ($2 Million/1 Year)

Head coach John Fox has raised some eyebrows with his refusal to commit to long-time starting quarterback Jay Cutler once he recovers from a sprained thumb because of Hoyer's steady play. Unfortunately for Hoyer, his contract doesn't contain incentives, like many backup quarterbacks have, that could boost his pay with extensive playing time.

Brian Hoyer might end up keeping the starting job in Chicago. USATSI

Josh Norman, CB ($75 Million/5 Years)

The NFL's highest-paid cornerback received widespread criticism after the season opener for not covering All-Pro wide receiver Antonio Brown all over the field. Norman isn't performing at quite the same level that earned him NFC Defensive Player of the Month honors last September with the Carolina Panthers but he is still Pro Football Focus' 11th highest-graded cornerback this season.

Adam Vinatieri, K ($6 Million/2 Years plus $1 Million in incentives)

The Colts re-signed the ageless wonder, who is in his 21st NFL season, in March. The 43-year-old Vinatieri is a perfect 8-for-8 on field goals, including three from beyond 50 yards, and hasn't missed an extra point either.

18. Miami Dolphins

Kiko Alonso, ILB ($4,300,401/4 Years)

Alonso was a part of an early offseason trade in which the Dolphins received the 13th overall pick in this year's draft from the Eagles in exchange for the eighth overall pick. After an injury-plagued and disappointing 2015 season in his comeback from a left ACL tear that sidelined him for the 2014 season, Alonso is starting to resemble the player that was named the Pro Football Writers Association's 2013 NFL Defensive Rookie of the Year.

Nick Fairley, DT ($3 Million/1 Year plus $1.75 million in incentives)

There isn't much to like about a porous Saints defense giving up the most points per game (32.5) and ranking next to last in total defense (422.8 yards per game). Fairley is providing a pass rushing presence from the interior of the defensive line with three sacks.

Alex Mack, C ($45 Million/5 Years)

The Falcons made Mack the NFL's highest paid-center for good reason. With Mack anchoring the offensive line, the Falcons have become the NFL's most explosive offense.

Alex Mack is at the center of the Falcons' offensive revival. USATSI

Kelechi Osemele, OG ($57 Million/5 Years & worth a maximum of $60 million with incentives)

Oakland's defense is a work in progress despite spending considerable resources in free agency to bring in linebacker Bruce Irvin, safety Reggie Nelson and cornerback Sean Smith. Although Oakland re-set the guard market with Osemele, he is paying immediate dividends by turning an already good offensive line into arguably the NFL's best.

Terrelle Pryor, WR ($1.671 Million/1 Year)

Pryor is making a lot of teams, including the New England Patriots, regret that they didn't sign him when he was out on the street before Cleveland signed him for the remainder of the season last December. The 6-4, 223-pound speedster is just scratching the surface of his talent in his transition from quarterback to wide receiver. Pryor has emerged as Cleveland's best receiving option with 15th-overall pick Corey Coleman out with a broken hand and Josh Gordon wearing out his welcome with the Browns.

Casey Hayward, CB ($15.3 Million/3 Years)

The addition of Hayward gives the Chargers one of the NFL's better cornerback units. Opposing quarterbacks are completing 56.3 percent of passes when targeting Hayward for a 40.9 passer rating according to Pro Football Focus. Hayward is tied for second in the NFL with three interceptions.

Lamar Miller, RB ($26 Million/4 Years)

Miller is a cheaper replacement for an injury-plagued Arian Foster, who was released from the final year of his five-year, $43.5 million contract, as the Texans' workhorse running back. Fourth in the NFL with 351 rushing yards, Miller has been up to the task.

Eric Weddle, S ($26 Million/4 Years & worth up to $29 million with incentives)

A change of scenery has revitalized Weddle after an acrimonious ending to his nine-year run with the San Diego Chargers. Weddle is performing much like the he did when earned All-Pro honors for five straight seasons (2010-2014).

Eric Weddle has been a hit in Baltimore. USATSI

Damon Harrison, DT ($46.25 Million/5 Years)

Harrison was signed to anchor a run defense that gave up 121.4 yards per game (24th in the NFL) on the ground in 2015. The Giants have improved to ninth in the NFL this season giving up 84 rushing yards per game.

Nick Perry, OLB ($5 Million/1 Year with additional $250,000 in incentives)

Perry's emergence has allowed the Packers to relegate 36-year-old Julius Peppers to spot duty in order to keep him fresher later in the season. He has 3.5 sacks in Green Bay's three games this season, which matches his 2015 regular season total in 14 games.

Christine Michael, RB ($725,000/1 Year with an additional $150,000 in incentives)

Seattle rolled the dice by not giving Michael a $1.671 million restricted free agent tender. Michael returned for less than half of that amount. Thomas Rawls was expected to be the successor to Marshawn Lynch, who retired, but he is out several weeks with a cracked left fibula. Michael is doing such a good job behind Seattle's shaky offensive line that there's no guarantee Rawls regains his role as the feature back when healthy.

Malik Jackson, DT ($85.5 Million/6 Years worth up to $90 million through salary escalators)

The Jaguars are off to slow start with a 1-3 record but Jackson isn't to blame. According PFF, he is second in the NFL among interior defensive linemen with 18 total quarterback pressures (combined sacks, quarterback hurries and quarterback hits).

DeMarco Murray, RB ($25.5 Million/4 Years & worth up to $32.9 million through incentives)

Murray was dealt to the Titans early in the offseason in an exchange of 2016 fourth-round picks after failing to live up to the five-year, $40 million contract (with $21 million in guarantees and worth a maximum of $42 million through salary escalators) he received from the Eagles in 2015 free agency. He cut $5.45 million out of the remaining four years of the base value of his contract to make the trade work. Murray is having a bounce-back year. He is fifth in the NFL with 340 rushing yards and averaging 5.2 yards per carry (tied for fourth in NFL).

DeMarco Murray has been a workhorse for the Titans. USATSI

Chandler Jones, OLB/DE-($3,194,500/5 Years with 2016 option)

Jones, who was acquired from the New England Patriots in March for a 2016 second-round pick (61st overall) and guard Jonathan Cooper, is the best pass rusher the Cardinals have had in quite some time. He is tied for third in the NFL with four sacks.

4. Buffalo Bills

Zach Brown, OLB ($1.25 Million/1 Year)

Brown is making the most of the opportunity provided by 2016 second-round pick Reggie Ragland's ACL tear. He is leading the NFL with 53 tackles.

3. Detroit Lions

Marvin Jones, WR ($40 Million/5 Years)

Jones is proving there is life after Calvin Johnson, who abruptly retired after the 2015 season. He is second in the NFL with 482 receiving yards and averaging 21 yards per catch.

Sam Bradford, QB ($17.5 Million/2 Years & worth up to $40.5 million with salary escalators and incentives)

Minnesota gave up a 2017 first-round pick and a 2018 fourth-round pick that can become a third or second-round pick under certain conditions to get Bradford from Philadelphia. The Vikings pulled the trigger on the blockbuster trade in the days leading up to the regular season after Teddy Bridgewater went down with devastating knee injury. Bradford, the No. 1 overall pick of the Rams in the 2010 NFL Draft, is playing the best football of his career in leading the Vikings to a 4-0 start.

Sam Bradford isn't making the Vikings regret pulling the trigger on the big trade to get him. USATSI

1. New England Patriots

LeGarrette Blount, RB ($1 Million/1 Year with an additional $950,000 in incentives)

Blount was named AFC Offensive Player of the Month for September because he helped keep the Patriots afloat while Tom Brady served his four-game suspension relating to Deflategate. He has the third-most rushing yards in the NFL with 352 and is tied for third with four rushing touchdowns while the Patriots sit atop of the AFC East with a 3-1 record.