The 49ers’ defense has been paramount to their first 3-0 start since the 1998 season. They held the Steelers to 20 points after the offense gave the ball to Pittsburgh five times. The defense faces their toughest test of the season when they square off against the Browns with quarterback Baker Mayfield, wide receiver Odell Beckham, and running back Nick Chubb.
Here are six players to watch when the defense is on the field:
DE Nick Bosa

The issue with Bosa hasn’t been getting to the quarterback, but finishing. He leads the 49ers with 17 quarterback pressures and just one sack to show for it. Baker Mayfield has been sacked 12 times this season behind a beat up offensive line so there will be chances for Bosa to make a huge impact.
CB Emmanuel Moseley

Moseley makes his first career start Monday and will likely draw a slew of matchups against Beckham. Moseley took over for Jason Verrett against for the Steelers after Verrett struggled on his lone drive of the game. The second-year corner will have his hands full against Beckham. Jarvis Landry and the speedy Antonio Callaway.
S Jaquiski Tartt

The Browns’ explosive pass catchers thrive on turning short throws into long gains. Tartt will be responsible for getting into the box to prevent big plays from the receivers and erasing them quickly after they make plays in the short and intermediate passing games. Tartt has been good in coverage this season, allowing only three receptions on seven targets.
CB Richard Sherman

With Moseley facing Beckham, Sherman will likely get Landry in what will be his toughest test since Week 1 against Mike Evans. The 49ers defense has been able to leave Sherman on his island with the improved pass rush, and he will have to play well to take his side of the field away from Mayfield and force the second-year quarterback into some mistakes on the other side.
S Jimmie Ward

Ward will likely make his 2019 debut Monday night. He might take the starting free safety spot from Tarvarius Moore. Moore played well, but allowed a few big plays in the first three games of the season due to his lack of experience. Ward could help improve an already impressive 49ers defense if he does get on the field and stays healthy.
DL DeForest Buckner

Buckner is most known for his ability to rush the quarterback, but the 49ers will need him to stop Browns RB Nick Chubb. Chubb has the power to get through a defensive line and the speed to run past the second level. Buckner will need to make a home in the Browns’ backfield to keep Chubb from getting into the second level clean. The quicker the 49ers can hit the second-year running back, the better. That’ll start in the middle with Buckner.