A short week was not kind to the San Francisco 49ers, as the team will be without key offensive pieces, including quarterback Brock Purdy, against the Los Angeles Rams on "Thursday Night Football."Wide receivers Ricky Pearsall and Jauan Jennings will also be unavailable for the 49ers on Thursday night.Purdy missed Weeks 2 and 3 after suffering a toe injury in the season opener but returned in Week 4 against the Jacksonville Jaguars. During the 26-21 loss, Purdy’s toe injury flared up again.CLICK HERE FOR MORE SPORTS COVERAGE ON FOXNEWS.COMIn turn, Mac Jones will make his third start of the season.He filled in for Purdy in the previous games, completing 66% of his passes for 563 yards with four touchdowns and one interception over that span. The 49ers won both of those games.49ERS LOSE STAR NICK BOSA FOR REMAINDER OF 2025 SEASON WITH TORN ACL: REPORTSJones is also dealing with a knee injury, but the 49ers said he was a full practice participant on all three of their injury reports this week. He has no game status heading into Thursday night.Jennings is battling ankle and rib injuries, while Pearsall has been limited by a knee issue. The 49ers will turn to receivers Kendrick Bourne and Demarcus Robinson, the latter of whom made his season debut last week after serving a suspension.San Francisco will also be without receiver Jordan Watkins (calf) and defensive end Robert Beal (ankle), while defensive tackle C.J. West (thumb) is questionable.This is already a pivotal game in the NFC West race, with both teams entering at 3-1 in the first of two matchups this season. The Rams bounced back last week with a win after a crushing loss to the Philadelphia Eagles, when two blocked field goals sealed the defeat.Matthew Stafford and the Rams’ offense have thrived, as the addition of Davante Adams to play alongside Puka Nacua and Kyren Williams has led to the fourth-most yards per game in the league this season.49ers head coach Kyle Shanahan will have to lean on star running back Christian McCaffrey and the accuracy of Jones to keep the Rams from pulling away.Follow Fox News Digital’s sports coverage on X, and subscribe to the Fox News Sports Huddle newsletter.