The last thing the San Francisco 49ers needed was another injury.

Already without almost two dozen players, plus coach Kyle Shanahan shaking off a concussion, the Niners couldn’t make it one drive in their first preseason game without losing another player.

Cornerback Jack Jones left during the Titans’ opening drive with a hand injury and was ruled out for the remainder of the game.

Jones, a fifth-year veteran, signed with San Francisco as free agent and had been a camp standout as a second-teamer in what has been the 49ers’ strongest unit so far.

The secondary had also been the 49ers’ healthiest group with only safety Malik Mustapha (hamstring) counting among the 17 players currently managing injuries. That should help if Jones is forced to miss time.

The 49ers did not specify the nature or the severity of Jones’ injury.

He left the game after helping run down Titans running back Tyjae Spears on a 25-yard gain on the eighth play from scrimmage of the game. Fourth-round rookie Ephesians Prysock replaced him.

Tennessee’s starters finished off the 95-yard scoring drive against the 49ers’ backups.

The 49ers’ second string offense answered with a touchdown drive, and third-string quarterback Kurtis Rourke completed 12 of 14 passes for 100 yards, but he later left, too, with a rib injury.

The Niners did not provide an immediate update on Rourke’s status.

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49ers injuries

• RB Kaelon Black (adductor)

• DE Nick Bosa (tendinitis)

• WR Jacob Cowing (hip flexor)

• LB Luke Gifford (hamstring)

• FB Kyle Juszczyk (finger)

• TE George Kittle (Achilles)

• RB Christian McCaffrey (tightness)

• S Malik Mustapha (hamstring)

• OL Brett Toth (concussion)

This story will be updated.