"They Amag management won't sell the company for $18, nor will long term shareholders -- the stock was recently $19 on its own," says the AMAG shareholder, who asked to remain anonymous because his fund doesn't permit him to speak to the media. " AMAG CEO Brian Periera doesn't get the big payout at these prices. In the $20s, they might be able to go hostile, direct to shareholders. What it does do is put a floor under the stock."

Another hedge fund manager, also unaffiliated with MSMB Capital, questions the legitimacy of the Amag offer.

"I don't know that MSMB has the financial resources to buy Amag, and if that's the case, this just feels like stock manipulation to me," says the fund manager, who also requested anonymity.

In its letter to Amag, MSMB Capital says a higher-priced offer for the company is possible contingent on due diligence. MSMB seeks a response from Amag by Aug. 15.

--Written by Adam Feuerstein in Boston.

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Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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