Sprint logoDespite having its best product launch day ever last month, Sprint was on the receiving end of some harsh criticism Tuesday. According to The Wall Street Journal, Greenlight Capital’s David Einhorn had some unpleasant words for the telecommunications company in a recent letter to investors.

In the letter, Einhorn devotes a long paragraph lambasting the way Sprint handled its iPhone launch. In addition, Einhorn goes how to condemn the Now Network for botching a much-anticipated investor meeting last month; Sprint later admitted it bungled the meeting.

The letter also expressed concern over Sprint’s management, saying they are “on the verge of losing the confidence of the financial markets,” despite raising billions from bond investors in a recent sale.

Greenlight also wrote, “We wouldn’t be surprised if shareholders begin to agitate for significant strategic change,” referring to the idea that Sprint may need a new owner.

If you play the market, it will be interesting to see how Greenlight’s words affect Sprint’s position among investors. The Overland Park-based company got what it wanted in the iPhone, but management can’t seem to put a foot right otherwise.

According to FactSet’s LionShares, as of June 30, 2011, Einhorn’s Greenlight Capital owned 55.9 million shares of Sprint.