Star striker Jimenez has been on the sidelines since suffering a fractured skull at Arsenal in November.
Boss Nuno Espirito Santo stated in February he was ‘totally confident’ the 29-year-old would play again in 2020/21.
But Darby, who worked at Wolves from 1986 until 1995, says him being involved over the final six Premier League games is not a guarantee.
“The actual fracture of the skull will be healed now. That won’t be an issue,” said Darby.
“It’s probably stronger than before as you have a build-up of new, strong bone around the fracture site.
“But it’s the trauma to the brain and unfortunately, you can’t play football without heading a ball.
“Of course, the Chelsea keeper, Petr Cech, wore protection for years afterwards.
“Matt Perry, Wolves’ doctor, is quite a renowned specialist when it comes to head injuries.
“The FA have used him as an expert many times, and he’ll be right on the ball with this one while also being, quite rightly, cautious.
“I would have thought Jimenez will get into pre-season, really, both for his fitness and his mental approach to everything. Having him in a controlled environment where they can ease him into games.”
Jimenez has spent the last couple of months taking part in training sessions at Compton – but they are yet to receive clearance for him to start heading balls again.
The Mexican has joined in with small-sided games, while avoiding contact, and also joined his national team for similar activities ahead of their game in Wales last month. He has worn a tailor-made headguard during that time.
“The headguard isn’t physically doing a great deal. It’s about your mental approach,” said Darby, who now runs a clinic in Albrighton.
“You could consider it like strapping. For years, we’ve put strapping on players’ ankles as they like the security.
“The feeling of it just gives them a bit of confidence. He’ll be doing non-contact ball work to gain his fitness, which is what he needs.
“But, sometimes, I see players where you just know they need a pre-season to get the full benefit out of them.
“I think he’ll be one of those, getting a gradual introduction through pre-season in a controlled environment.”
Nuno, speaking last Friday before the 1-0 win against Sheffield United, revealed Jimenez has been working ‘in the same circumstances as previous weeks’.
When asked if injuries to team-mates Jonny Castro Otto and Pedro Neto mean they are now being more cautious with the forward, Nuno said: “That doesn’t have anything to do with the others. All the aspects of the injuries are separate.
“They are totally individual circumstances. In the case of Raul, we have to wait. Raul is still working with us in the same circumstances as previous weeks.
“He doesn’t head the ball, but he’s been able to join almost all of the training sessions. He’s ready, he’s well, but we still have to wait on the medical decision for him to take part in the games.”