Driven by the prospect of a 2013 San Francisco America's Cup and Salesforce.com's recent $278 million land acquisition in nearby Mission Bay, the Port of San Francisco received an unexpectedly strong group of developers looking to take on one of the most challenging redevelopment plays in recent memory.

Pier 70, a big commercial development project south of AT&T Park, has drawn the interest of major South Bay developer The Sobrato Organization. It would be the developer's first venture in San Francisco, partnering with TMG Partners in a 50-50 joint venture.

TMG President Michael Covarrubias said, "(Sobrato's) breadth of tenants in the South Bay is staggering. We believe the migration for Silicon Valley companies to San Francisco will continue, and there are not too many places you can put 3 million square feet."

At stake is a major commercial opportunity in San Francisco: 3 million square feet of new office development, 700,000 square feet of rehabilitated historic space, 20 acres of open space, and 6,000 to 8,000 jobs.

The Sobrato family, which owns 8 million square feet of office space and 7,300 apartment units, is worth $2.5 billion, according to Forbes Magazine. Sobrato built the Apple Inc. and Netflix Inc. headquarters. The Sobrato Organization did not comment by press time.

"What a range of choices and very credible respondents," said Gabriel Metcalf, executive director of the San Francisco Planning + Urban Research Association. "I think this is very promising. The proposers are quite different so the port has a lot of different options to choose from. The proposals are from people who know how to do this. These are serious."

Covarrubias said they were very much motivated by the Salesforce deal in Mission Bay, where the cloud computing giant bought most of the remaining developable land.

Other prospective developers are Build Inc., which developed the Homes on Esprit Park project; Pacific Waterfront Partners, which redeveloped Piers 1½, 3 and 5 and is working with architect Skidmore Owings & Merrill; and the Mission Bay Development Group, a spinoff of Farallon Capital Management that is overseeing the redevelopment of Mission Bay. Phil Owen, president of Mission Bay Development Group, said it is working with equity partner Cherokee Capital, architect Perkins + Will, and Nibbi Construction.