At this point, it's well known that Christian McCaffrey is dealing with Achilles tendinitis, but what's not so well known is how the injury happened. The 49ers running back missed most of training camp due to what was termed a "calf" issue, but the team never offered any details about how he suffered the injury.   

During an interview on the "Ross Tucker Football Podcast," McCaffrey's dad, Ed, shed some light on how his son got injured. 

"Tendinitis is an over-training injury, meaning you're training too hard or doing too much, and it turns into tendinitis," Ed said, via NBC Sports Bay Area. "If I would say that Christian has a weakness, it's that he sometimes has to protect himself from himself, in terms of training too much and doing too much."

The younger McCaffrey is notorious for his brutal offseason training, and as Ed said, it appears that this was the root cause. The 49ers running back originally was experiencing Achilles tendinitis in just one of his legs, but by the time September rolled around, he was dealing with it in both legs. Ed offered an explanation for why that happened. 

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"It started with one, then it creeps into your calf and you start overcompensating and then you start feeling it in the other one," Ed said. "It's just tendinitis. It just means it's very, very sore."

That soreness hasn't gone away, which is a big reason why the younger McCaffrey flew off to Germany in September. The 49ers running back was looking for some advice on how to get the injury to heal faster. 

"He trusts his 49ers training staff,but when the prescription is just to rest, he's going to go out and get other professional opinions from people around the world," Ed said of the trip to Germany. 

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As things stand now, it's still not clear when McCaffrey might return to the line up. 

"If you have tendinitis, you have tendinitis," Ed said. "I think of it as tennis elbow. You see tennis players get it, and they can't play tennis for a while until it heals up.

49ers coach Kyle Shanahan admitted last week that there's no set timeline for when McCaffrey might return, but the team is hoping to have a better idea at some point in the near future. 

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"I think we'll get a better idea here over the next couple of weeks," Shanahan said. "The whole point of putting him on IR is to guarantee that we couldn't do anything for at least four weeks. And two weeks into it, the whole point was just to rest him for two weeks and not do that."

McCaffrey is eligible to be activated off IR after Week 5, but at this point, it seems unlikely that it would happen that soon. The team does have a Week 8 bye and it's possible that it would make more sense to target that as a possible return date. That means McCaffrey wouldn't return to the field until Nov. 10 (Week 9 vs. the Buccaneers), which would give him another month to heal. If he can't return by that date, then it would definitely start to feel like that there's a chance he could miss the entire season.