The space is one of the biggest blocks of office space to come on the market at the Prudential Center in years, realtors say. "We can restack some of the floors at the Pru or move to office space at the South Boston manufacturing facility," says the spokesman, noting that the company's decision to reconsider its space needs was prompted by a wave of relocations and job cuts.

Richards Barry Joyce & Partners, which is working to sublease the space for Gillette, declined to comment citing a confidentiality agreement with the firm. But Rick Lowe, a principal with Cresa Partners in Boston, tells GlobeSt.com that such a large chunk of office space on the market could loosen up the office market and stabilize rents in the Back Bay. The Back Bay has become one of the hottest office markets in the city in recent quarters.

Subleasing that space, however, could prove challenging for Gillette since the company's lease with Boston Properties, which owns the building, only extends to 2009, Lowe says. "It's going to be a challenge because of the short term," he says, adding he anticipates it will take 18 to 24 months for the market to absorb such a large chunk of office space. But if priced right, he notes, it could also present an opportunity for value-minded companies to get cut-rate space at one of the Back Bay's most prominent addresses.