Apple CEO Tim Cook. Apple One of the key designers behind some of Apple's most daring Mac products in the past few years has moved to Tesla to work on electric cars.

Matt Casebolt, who had worked on the Mac Pro and the new MacBook as a director of product design at Apple, said on his LinkedIn profile that he started as a director of engineering for closures and mechanisms at Tesla in December.

9to5Mac first reported the news, saying he had actually led the team working on the Mac Pro.

Casebolt, judging by his patents, was a member of Apple's elite design team, which historically has very low turnover. The small group used to be headed by Apple's chief design officer, Jony Ive, but it has apparently been going through leadership changes recently.

Tesla CEO Elon Musk has previously called Apple "the Tesla graveyard" based on its supposed proclivity to hire Tesla employees who didn't work out. But the talent movement goes both ways, especially after Apple reportedly retrenched and downscaled its electric-car project.

One of the key goals of Apple's electric-car project was reportedly to retain top talent.

Casebolt's job change comes a day after Chris Lattner, one of Apple's most visible directors as its head of developer tools and creator of its programming language, Swift, announced that he was headed to Tesla to head software for self-driving cars.

Y Combinator, Silicon Valley's premier startup incubator, also announced on Monday that Daniel Gross, who had worked on machine learning at Apple after it bought his startup, would be joining Y Combinator as a partner.

A big company

Tesla CEO Elon Musk. Bill Pugliano/Getty Images After Lattner's announcement on Monday, Apple observers predictably started to speculate about what it meant for the company and whether Apple may have a problem retaining talent.

Casebolt's newly publicized move will only add fuel to the fire.

While highly paid directors and managers leaving a company is never a good sign, it's important to understand that Apple is a huge company. Out of 116,000 employees, some are bound to leave from time to time.

But there are signs that Apple's approach to talent may be hitting a strained point. Apple announced through a Securities and Exchange Commission document last Friday that it had missed internal, still-secret targets for 2016. Apple executives lost compensation because of the missed targets.

Apple, which has grown prodigiously over the past five years, may be slowing its growth on the rank-and-file and preventing managers from building teams as large as they were even a few years ago.

Apple added 6,000 full-time employees in 2016, according to SEC documents. That was down from 2015, when it added 17,400 employees. Apple reportedly scaled back its contract recruiting as well, according to a Venturebeat source.

Message boards around the internet are filled with unconfirmed speculation about hiring freezes and stories about successful interviews without job offers because Apple has significantly slowed hiring.

Apple is still a coveted place to work, and most of the Apple people whom I have spoken with love their jobs and the company they work for. It's too early to say that Apple may be having trouble retaining important engineers. But Apple's not the only game in town, and it has lots of employees whom other Silicon Valley companies would love to have.

Apple is expected to move its executives and lots of employees into its new campus early this year.

Know anything about hiring at Apple? Email the author at kleswing@businessinsider.com.