The San Francisco 49ers have invested heavily in the defensive line the past four years, but the player to watch in 2018 might be a player acquired via the waiver wire. From 2015 to 2017, the 49ers three consecutive first round picks on the defensive line, drafting Arik Armstead, then DeForest Buckner, then Solomon Thomas. However, their November 20, 2017 waiver addition of Sheldon Day is the one to watch in my mind.

Over the past two weeks of camp, Day has reportedly impressed. Matt Maiocco and Matt Barrows both noted a strong play he had on Friday in which he sliced into the backfield to stop running back Matt Breida for a five-yard loss. Maiocco noted a sack he had on the next snap, while Barrows said it has felt like Day has made at least one highlight play per practice in camp. Barrows noted his ability to knock down passes, even as one of the shorter defensive linemen on the roster.

Arik Armstead and Solomon Thomas are more high profile given their first round status, but Day could find some big opportunities soon. Armstead is sidelined with a hamstring injury, and could miss several weeks. The 49ers have a lot of options on the line, but I suspect Day emerges as the primary rotational guy behind Buckner and Thomas.

The Jacksonville Jaguars surprised some folks when they waived Day, a 2016 fourth round pick. The 49ers had the No. 2 waiver priority at that point, and they used it wisely. The team claimed Day on November, and two days later they claimed edge rusher Cassius Marsh.

Day quickly moved into the defensive line rotation quickly, playing 30 defensive snaps in Week 12. DeForest Buckner, Solomon Thomas, and Earl Mitchell all played more snaps, while Arik Armstead was on IR at that point. By season’s end, Day was out-snapping Mitchell. They played different versions of defensive tackle, but the move to get Day more work showed the growing trust.

Day is now entering the third year of his rookie contract, which means the 49ers can negotiate a new deal after this coming season. The 49ers exercised Arik Armstead’s fifth year option for 2019, but his future with the 49ers is a big question mark. If Day can excel this year in a growing role, I could very well see the team try and extend him before next season.