The San Francisco 49ers ruled out quarterback Brock Purdy and three receivers for Thursday night's game against the Los Angeles Rams. The depleted offense will rely on Mac Jones at quarterback while facing one of the league's top defenses.

San Francisco ruled out Purdy (toe), receivers Jauan Jennings (ribs, ankle), Ricky Pearsall (right knee) and Jordan Watkins (calf) on Wednesday. Tight end George Kittle (hamstring) and receiver Brandon Aiyuk (knee) remain sidelined from previous injuries.

Jones will make his third start in the first five games after leading the 49ers to victories over New Orleans and Arizona in Weeks 2 and 3. He recovered from a knee sprain suffered against the Cardinals and did not appear on this week's injury report.

"At the end of the day, you just have to ask yourself if you can protect yourself in the game, and I felt good to go," Jones said.

The 49ers' healthy active roster receivers include Demarcus Robinson, Kendrick Bourne, Skyy Moore and Marquez Valdes-Scantling. San Francisco will likely elevate Russell Gage Jr. or Malik Turner from the practice squad while also promoting backup quarterback Adrian Martinez.

Pearsall and Jennings both suffered new injuries during Sunday's loss to Jacksonville. Pearsall landed hard on his right knee while Jennings took a significant hit to the ribs catching a 2-point conversion.

The Rams defense ranks ninth in yards allowed per game (284.5), fifth in defensive expected points added (13.78) and tied for second in sacks (14). Jones acknowledged the difficult assignment ahead.

"There's always 11 guys on the screen, and they have a great defensive line," Jones said. "They play a lot of different schemes. They do a lot of stuff but do it well."

San Francisco also ruled out defensive end Robert Beal Jr. (ankle) and listed defensive tackle CJ West (thumb) as questionable. The 49ers travel to play the Tampa Bay Buccaneers in Week 6 following Thursday's contest.