​The San Francisco 49ers are exploring options to bolster their backfield depth, holding workouts for veteran running backs Nyheim Miller-Hines and Zamir White on Monday, while also hosting free agent running back Blake Watson on an official visit, according to the NFL transaction wire.The roster evaluations come at a critical time for San Francisco’s offense. Superstar running back Christian McCaffrey was sidelined during Monday’s practice due to tightness. With a joint practice scheduled this week alongside the preseason opener against the Tennessee Titans, head coach Kyle Shanahan and his staff are unlikely to risk any of their top rotational backs in exhibition action.With McCaffrey, Jordan James, Kaelon Black, and Isaac Guerendo currently sidelined or working through injuries, the only healthy running backs remaining on the active roster are Patrick Taylor Jr., Sincere McCormick, and Khalil Herbert.Speaking on the team’s rotational shifts on Monday, offensive coordinator Klay Kubiak noted, “Anytime guys are out, it lets guys step up and gives them opportunities.”Here is a closer look at the three backs on San Francisco’s radar:Blake Watson: An undrafted free agent out of Memphis in 2024, Watson stands out as a strong candidate for a quick signing given that his Monday stop was an official visit. During his 2024 Pro Day, Watson posted elite athletic numbers, including a 4.39-second 40-yard dash, a 41.5-inch vertical jump, and an 11-foot-3-inch broad jump. Watson caught the 49ers’ attention in last year’s preseason while playing against San Francisco, turning in multi-tackle-breaking gains of 16 and 18 yards.Nyheim Miller-Hines: A fourth-round selection by the Indianapolis Colts in the 2018 NFL Draft, Miller-Hines spent five productive seasons in Indy before a July 2023 jet ski accident resulted in torn ACL and LCL injuries. After brief stints with the Los Angeles Chargers and New Orleans Saints last season, the versatile 29 year old offers extensive pass-catching and return capabilities.Zamir White: Drafted in the fourth round by the Las Vegas Raiders in 2022, the 6-foot, 215 pound power back posted his best statistical campaign in 2023, logging 451 rushing yards and 98 receiving yards. White saw limited action with Las Vegas last season, recording 12 carries.With snaps up for grabs during joint practices and preseason play, any incoming back will have an immediate opportunity to stake a claim on a practice squad role or a roster spot in San Francisco’s backfield.