Before being sidelined with a hamstring injury in the San Francisco 49ers‘ third game of the season — against the Seattle Seahawks — Jimmie Ward was one of the best defensive backs in the league. According to Pro Football Focus, Ward was the 9th best DB in the NFL with a rating of 82.6. Losing their best DB leaves a big hole for the 49ers, who were able to use Ward in both the slot and on the outside. Tramaine Brock, the 49ers’ second cornerback, has struggled to start the season, ranking 70th in PFF rankings with a 52.9 grade.

Ward’s replacement options come down to either rookie Rashard Robinson or third year corner Keith Reaser. Robinson has been impressive in his rookie season being used as a starter on the outside when the 49ers face three receiver sets. He’s played a total of 45 snaps at CB, posting a PFF grade of 72.8.

Reaser is right behind Robinson with a 71.4 grade in 54 snaps. The majority of those snaps — 47 — came in the Seattle Seahawks game, when Ward pulled his quad and Robinson was out with a stinger. Although the 49ers are only losing around 10 to 11 PFF points with Ward being out, the bigger question is if Robinson or Reaser can have an impact in the run game.

Ward is a hard hitter who thrives against the run and withDallas Cowboys wide receiver Dez Bryant questionable and starting quarterback Dak Prescott, the 49ers are sure to get a heavy dose of running back Ezekiel Elliott. The 49ers’ run defense needs to improve tremendously if the Niners are going to have a reasonable chance against the run-heavy Cowboys.