Free-agent finds for Week 13: David Johnson, RB handcuffs and Gronk replacements

David Johnson has seven offensive touchdowns on his 54 touches, and also this kickoff return TD in Week 2 against the Bears. AP Photo/David Banks

That went by quickly. December is here, and for many ESPN.com fantasy football leagues, Week 13 marks the final week of the regular season. While it's difficult to apply sweeping generalizations to fantasy football teams, one thing is true, in general: If your team is headed toward the playoffs right now, this isn't the time to jumble your lineup. You likely got to the playoffs on the strength of your studs, and the postseason isn't the time to overthink lineup decisions: Dance with the ones that brought you. But one critically important roster move (or moves) to make right now is to ensure that you have the insurance for your top players, especially at running back: their handcuffs.

With that in mind, part of this column will be dedicated to the top handcuffs, followed by our customary waiver-wire adds for Week 13. (Note: All players on this list are available in at least 50 percent of leagues.)

Notable handcuffs

David Johnson, RB, Arizona Cardinals (22.7 percent): Johnson tops this list because he might be needed right away, as both Chris Johnson and Andre Ellington left Arizona's Week 12 win over San Francisco with injuries. Chris Johnson has a broken tibia, according to ESPN NFL Insider Adam Schefter, while the timetable on Ellington's return is less clear. David Johnson, a talented third-rounder in the 2015 NFL draft, would likely see a significant role if Ellington sits in Week 13.

Jerick McKinnon, RB, Minnesota Vikings (3.8 percent): Adrian Peterson is still the best running back in football, and right now it isn't close. He's the most valuable player in the fantasy game right now too. McKinnon averaged 4.8 yards on 113 carries with Peterson out for almost all of 2014. All Peterson owners should invest in him.

Tre Mason, RB, St. Louis Rams (9.3 percent): A promising rookie in 2014, Mason has taken a back seat to Todd Gurley. But the talent remains, and the offense is decidedly run-oriented. Mason should be owned by all Gurley owners.

Bilal Powell, RB, New York Jets (12.8 percent): Powell already has a role in the Jets' offense, as he has 17 touches in the past two games. Chris Ivory had a resurgent Week 12, but Powell would be the next man up for the Gang Green offense.

Markus Wheaton, WR, Pittsburgh Steelers (7.6 percent): Wheaton is coming off of a monster nine-catch, 201-yard, one-touchdown game in Week 12, but he's still not a player that I'm finding room for in my starting lineup yet. The outing highlighted that Wheaton is a talented player (a former third-round pick) who would be relevant if something happened to Antonio Brown or Martavis Bryant.

Jay Ajayi, RB, Miami Dolphins (14.0 percent): Ajayi has established a role in the four games that he has played this season, totaling 24 touches in that stretch. He's a big (6-foot, 228 pounds) and talented back who slipped in the draft because of injury concerns.

Daniel Herron, RB, Indianapolis Colts (1.0 percent): With Ahmad Bradshaw placed on injured reserve Monday, Herron -- presumably -- takes over top reserve duties in the Colts' backfield. Frank Gore owners should add Herron.

Scott Chandler, TE, New England Patriots (2.0 percent): It was a hold-your-breath moment when Rob Gronkowski left the game Sunday night against the Broncos in what looked like considerable pain. The early word is that Gronk's injury may not be as serious as it may have looked, but Chandler steps into a starting role for as long as Gronk sits (Adam Schefter reports Gronk is likely to miss multiple weeks). He'd be a viable top-10 tight end.

Other notable adds

Dontrelle Inman, WR, San Diego Chargers (7.7 percent): The Chargers got back on track in Week 12, and part of that was because of the play of Inman, who had five catches for 65 yards and a touchdown. This offense's ceiling is too high to ignore the No. 2 wideout. He's a viable add for 12-team leagues and has even more value in point-per-reception (PPR) scoring.

Doug Baldwin, WR, Seattle Seahawks (33.9 percent): He has at least six catches in his past three games, including a monster Week 12 with three touchdowns. Baldwin is the No. 1 pass-catching target for Seattle with Jimmy Graham out for the season. Russell Wilson has been red-hot of late too. Baldwin is an add in 12-team leagues or larger.

Shaun Draughn, RB, San Francisco 49ers (35.1 percent): If you need a running back who can contribute now, Draughn is close to the only option who is widely available. He played every snap for the 49ers on Sunday, managing 20 touches. He is a usable option for those in PPR leagues.

Theo Riddick, RB, Detroit Lions (33.9 percent): Riddick is listed as a running back, but he produces like a wide receiver. He's up to 55 catches this season (almost twice as many as his 28 rushing attempts) and is a usable PPR back.

Anquan Boldin, WR, San Francisco 49ers (48.6 percent): Boldin is just steady. He has 13 catches for 186 yards in the past two weeks. He's a low-ceiling, medium-floor add in 12-team leagues or deeper. He has just two touchdowns this season, but is another player to keep in mind for PPR leagues.

Alex Smith, QB, Kansas City Chiefs (38.8 percent): Let's look back and then look forward for Smith: He has averaged 18.75 points per game in his past four outings. His remaining schedule is enviable (Oakland twice, San Diego, Baltimore and Cleveland). The play isn't to add Smith as your starter, but rather as insurance in case your starter misses time.

DeVante Parker, WR, Miami Dolphins (4.8 percent): Play in a super-deep league and looking for a name with talent? Parker fits the bill. His best value is still for keeper or dynasty leagues. Rishard Matthews left Sunday's game early because of injury. Parker's workload is likely to increase until Matthews comes back.

Other Gronk fill-ins

Jacob Tamme, TE, Atlanta Falcons (23.8 percent): Wide receiver Leonard Hankerson has missed three of the Falcons' past four games. In those games, Tamme has racked up 21 catches for 233 yards and a touchdown.

Kyle Rudolph, TE, Minnesota Vikings (21.0 percent): He has 13 catches and a touchdown in the past two weeks. The Minnesota passing offense isn't electric, but Rudolph is a quality red zone target given his size.

Zach Miller, TE, Chicago Bears (24.8 percent): Has four total touchdowns in his past four games. If Martellus Bennett is out again in Week 13, Miller is usable.

Vance McDonald, TE, San Francisco 49ers (0.6 percent): An athletic player now assuming a larger role with Vernon Davis in Denver, McDonald has 10 catches for 140 yards and two touchdowns in two games.

Crockett Gillmore, TE, Baltimore Ravens (22.7 percent): An athletic tight end who is among the top pass-catchers for Matt Schaub in Baltimore right now.

Brent Celek, TE, Philadelphia Eagles (9.9 percent): He has 27 fantasy points in his past three games. Zach Ertz missed the Thanksgiving game because of injury.

Cameron Brate, TE, Tampa Bay Buccaneers (0.0 percent): A pair of touchdowns to go along with eight catches for 100 yards during the past two weeks is enough to put the Bucs' young pass-catcher on our radar.