49ers’ Mitchell learns to not invite injuries after gaining lots of yards but taking big hits

New San Francisco 49ers running backs coach Anthony Lynn had some advice for Elijah Mitchell this spring after reviewing his historic rookie season.

Lynn, a former NFL running back, was impressed with Mitchell’s aggression, decisiveness and fearlessness. The advice: When possible, avoid collisions instead of inviting them.

“At least take half a man,” Lynn said, smiling. “That’s better than taking the whole man.”

Mitchell’s penchant for full-speed, pile-moving collisions was a reason for his dazzling debut.

Mitchell, a sixth-round pick, set a franchise rookie record for rushing yards (963) and ranked second among all NFL rookies in that category, trailing only Steelers first-round pick Najee Harris.

However, Mitchell, who played at Louisiana, discovered that the NFL is several steps up in physicality from the Sun Belt Conference. Mitchell crammed a career’s worth of agony into one season: He had an injury that required an in-season surgery (broken finger), an injury that led to an offseason surgery (knee), a sprained shoulder, a concussion and he suffered multiple broken ribs after missing a few weeks of training camp with

Stephen Lam / The Chronicle