Sometimes the NFL's top plays on a Sunday come from people we wouldn't expect. They're the plays that make you ask, "Who was that?" These performances can change a player's career.
Here's a look at Week 16's unheralded ballers, starting with a pair of replacement linebackers who helped the Patriots and Rams clinch something special.
Team-high 10 tackles, 2.5 sacks in 37-16 win over Bills
What happened: Flowers' biggest play came on a fourth-and-2 tackle of Tyrod Taylor as he scrambled to the right sideline. It was a huge turnover on downs.
Why it matters: The Patriots are thin at linebacker, but Flowers showed up in a big way. He didn't have a sack entering the game. He has earned more playing time going into the playoffs. The Patriots clinched a first-round bye.
Interception and sack in 27-23 win over Titans
What happened: Littleton got a great drop into his zone and made a play on the ball when Marcus Mariota tried to throw it over his head. Littleton also took down Mariota later in the game.
Why it matters: Littleton is a backup linebacker more known for his two blocked punts this season, but he stepped up as a defensive playmaker in place of the injured Mark Barron. The Rams clinched the NFC West.
Damiere Byrd, KR/WR, Carolina Panthers
103-yard kick return TD in 22-19 win over Bucs
What happened: Byrd ran up the gut, broke a few tackles and glided along the right sideline for the Panthers' first TD to put them up 12-6.
Why it matters: The Panthers had to claw to a win against the Bucs, and who knows if it would've happened without Byrd's big return. It clinched a playoff spot for Carolina.
Pick-six of Tom Brady in 37-16 loss to Patriots
What happened: Poyer made a great read and jumped a Brady pass for the diving interception. He got up and took it to the house.
Why it matters: There was frustration among the Bills after Poyer didn't get Pro Bowl recognition, but plays like that one on Brady will give you national recognition.
Emergency long-snapper duties
What happened: Vikings long-snapper Kevin McDermott suffered a shoulder injury, and Morgan stepped up to complete his duties despite never having done so in an NFL game before.
Why it matters: The cliché of "next man up" is challenged when a position has no backup. Morgan shifted over at long-snapper as though it was nothing and provided a much-needed effort as the Vikings fought for a first-round bye.
NFL Nation reporters Mike Reiss and Courtney Cronin contributed to this story.