The 49ers are fearing a diagnosis of a torn ACL for rookie wide receiver Shawn Poindexter, coach Kyle Shanahan said on Tuesday.

Poindexter, an undrafted player from Arizona, sustained the knee injury on a special-teams play in the second half of Monday night's preseason win over Denver. He was scheduled to undergo an MRI examination to confirm the extent of the injury.

Poindexter (6-foot-5, 213 pounds) played just one snap of offense and four plays of special teams on Monday. In the opener, he caught two passes for 12 yards against the Dallas Cowboys. Poindexter appeared to be a prime candidate to land a spot on the 49ers’ practice squad this season.

The club is prepared to re-sign wide receiver Chris Thompson to take Poindexter’s spot on the roster, Shanahan said.

In other injury news, neither running back Jerrick McKinnon nor defensive end Dee Ford is expected to return to practice this week on a short week before the 49ers face the Kansas City Chiefs on Saturday. Both players underwent recent platelet-rich plasma treatments for their knees. McKinnon has been slow to return from a torn ACL of nearly a year ago, while Ford experienced tendinitis in his knee early in training camp.

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The 49ers are hopeful center Weston Richburg to will be able to practice next week and possibly play in the team’s final preseason game against the Los Angeles Chargers. Richburg had extensive surgery on his knee and quad in the offseason after playing most of last season with the injuries.