FORTUNE — Last August, Andy Miller stepped down as Apple’s mobile ad boss to join venture capital firm Highland Capital Partners as a general partner. Now he’s leaving Highland to serve as president and chief operating officer of Leap Motion, a Highland portfolio company that makes 3D motion-control and motion-sensing technology.

“Andy had been spending around 80% of his time on Leap over the past few months anyway, and he brought up the idea of going there fulltime,” says Peter Bell, a general partner with Highland. “We talked about it a lot, and think it’s the right move for Andy, the company and Highland. This is one of those companies that really feels different, and having Andy there makes us feel even better about it.”

But make no mistake, this is still a big hit for Highland from an organizational standpoint. The Cambridge, Mass.-based firm had spent much of last year trying to find a new partner who could really help boost its profile in Silicon Valley. Getting Miller was viewed as a coup, and losing him — even to a Highland portfolio company — may make it more difficult for Highland to attract West Coast entrepreneurs.

Bell says he understands the concern, but doesn’t share it. He points out that Miller will continue to represent Highland on certain boards, and provide deal-flow to the firm. Moreover, Highland recently buttressed its Menlo Park office by hiring Manish Patel from Google and relocating Alex Taussig from Cambridge. Bell also said that the firm has no plans to hire a new West Coast partner to replace Miller.

Miller had joined Apple in 2010, after it paid $275 million to purchase Quattro Wireless, a company Miller had co-founded and run.

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