The story of the San Francisco 49ers season may be perfectly summarized by their struggles in the offensive backfield.

Injuries have plagued them since training camp when running back Christian McCaffrey was shut down because of Achilles tendinitis that wound up costing him the first nine weeks.

Another knee injury to McCaffrey and a high ankle sprain for RB Jordan Mason in the team’s Week 13 loss pushed the 49ers to third-string rookie RB Isaac Guerendo to start Week 14. He played well, but sprained his foot in the win over the Chicago Bears.

Guerendo returned despite a quick turnaround to a Thursday night game vs. the Los Angeles Rams in Week 15, but he wound up sustaining another injury during the 49ers’ 12-6 loss.

Head coach Kyle Shanahan on Wednesday in a press conference told reporters Guerendo sustained a hamstring injury against the Rams.

This is a pretty sizable red flag since hamstring issues plagued Guerendo in college and cost him most of training camp. His status for Sunday’s matchup with the Miami Dolphins is unclear, but it wouldn’t be a surprise if the 49ers are conservative with their fourth-round pick.

The 49ers have only three games left and their postseason hopes are effectively extinguished. Guerendo has performed well enough in his two games to give some optimism about his future in the 49ers’ backfield. San Francisco may not want to risk any long-term damage in the name of winning a Week 16 game in a lost season.