The Blackstone Group clinched the hard-won Equity Office Properties Trust (EOP) portfolio about 48 hours ago. How’s this for a multi-billion dollar office flip? On this quiet Friday afternoon at the tail end of (another) bruising week of deal making, Blackstone has sold $7 billion of the EOP Manhattan portfolio to local player Harry Macklowe. Rumors of this side deal were first reported in the Wall Street Journal yesterday.

The deal gives local investor Macklowe another 6.5 million sq. ft. of Manhattan office space. The properties are 717 Fifth Avenue, Worldwide Plaza, 1301 Avenue of the Americas, Park Avenue Tower, 527 Madison Avenue, 1540 Broadway, 850 Third Avenue and Tower 56. In a press release, Harry Macklowe called the acquisition “a synergistic compliment” to his existing portfolio. Macklowe already owns about 6 million sq. ft. of Manhattan office space, chiefly in the high rent Midtown district, so this deal will more than double his sizeable New York footprint.

Market watchers expect Blackstone to part with even more EOP assets over the next few weeks. Real estate investor Larry Fiedler, president of JRM Development Enterprises, wouldn’t be surprised if some assets were sold to Vornado Realty Trust and its unsuccessful bidding partners, Starwood Capital and Walton Street Capital.

“Vornado and Walton Street have [probably] made deals with Blackstone [already]. Blackstone is not an operator,” says Fiedler, who formerly taught at New York University’s Real Estate Institute.

Fiedler expects Vornado to pursue EOP’s Irvine, Calif. portfolio. The investor believes there’s a lot of upside to that portion of the empire, and he also sees Vornado as the perfect buyer for these assets.

“That stuff needs the type of effort that is right up Vornado’s alley,” he says.

Just how many more EOP assets will Blackstone shed? Fielder estimates that as much as 25% of the portfolio — or 25 million sq. ft. of office space — could be shorn off in coming weeks.