This Executive is Alibaba Chairman Jack Ma's Alter Ego

Bill Gates had Steve Ballmer, Steve Jobs had Tim Cook, and Mark Zuckerberg has Sheryl Sandberg. Travis Kalanick desperately needs the executive who completes him.

One person I barely was able to mention in my recent feature about Alibaba's Jack Ma is Joe Tsai, the company's vice chairman and Ma's indispensable right-hand man and alter ego.

If Ma is now a global business superstar, Tsai is as famous in the investing community that has interacted with Alibaba. He is the Taiwanese-born, U.S. prep-school and Yale-educated corporate lawyer and private-equity investor who signed on early with Alibaba and helped make the Chinese e-commerce giant the business it is today.

Alibaba (baba) the company is known for its swagger. Yet Ma and Tsai, each in their own way, are the pictures of humility. Ma readily admits to expertise in neither technology nor dealmaking, the latter being Tsai's purview.

I interviewed Tsai last month, and he described how he joined Alibaba.

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"It was a time before we had raised any outside capital, and Jack hadn't even incorporated the company yet," said Tsai. "And he said to me that, 'Look Joe, I don't know anything about finance or law, and I need to incorporate a company. I need to make sure that there's an agreement among all the founders as to how we run the business going forward. And I need to make sure that we can go out and raise capital. I don't know how to do any of this. So, why don't you come in and help me?' "

Tsai left a cushy private-equity gig in Hong Kong to do as Ma asked. He's a billionaire now. And as happy a No. 2 as they come.