Christian McCaffrey’s dad has claimed the San Francisco 49ers star developed his Achilles tendinitis injury by running himself into the ground in practice.

McCaffrey, 28, is currently suffering from bilateral Achilles tendinitis – meaning he is dealing with the issue in both of his legs – with his return date still unknown.

The star running back recently hopped on a flight to Germany to undergo treatment for the problem, which has kept him out since Week 2 of the new NFL season.

There are fears that McCaffrey could be kept on the sidelines for a couple of months as he undergoes a lengthy recovery.

According to his father, former San Francisco wide receiver Ed, the injury comes from working too hard on the practice field.

‘Tendinitis is an over-training injury, meaning you’re training too hard or doing too much, and it turns into tendinitis,’ Ed said on the Ross Tucker Football Podcast.

‘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.’

Achilles tendinitis is described by the Mayo Clinic as ‘an overuse injury of the Achilles tendon, the band of tissue that connects calf muscles at the back of the lower leg to the heel bone.’

Most cases can be treated with at-home care, while more serious cases can lead to Achilles ruptures that might require surgery.

The Niners said they expected to get a ‘better idea’ on McCaffrey’s status in the course of the next few weeks – with the plan to ramp up his rehab to see how his body will respond.

‘And now, we’re going to start hitting the rehab harder and trying to get him back into football stuff and see how it responds,’ Niners head coach Kyle Shanahan said last week. ‘So we’ll see how he responds here. We’ve let him rest here for a couple of weeks.’

It’s not clear when McCaffrey is expected to be back – with ESPN’s Adam Schefter reporting that even the running back himself is unaware of when he’ll return.

‘I don’t think Christian McCaffrey knows when he’s coming back. I don’t think the 49ers know when he’s coming back. I don’t think anyone knows right now when he’s coming back,’ Schefter said Monday on ‘The Pat McAfee Show.’

‘They are going to begin to ramp up Christian McCaffrey, potentially even this week, starting to get him back to see how he’s feeling.

And ideally, you’d like to hope and think that he’s feeling better — that the time off will have helped — but who knows how the calf and Achilles is going to react. Nobody can say for certain.’