By Ryan Vlastelica

NEW YORK (Reuters) - U.S. stock index futures pointed to a flat open on Tuesday after data showed the U.S. economy grew in the third quarter, but at a slower-than-expected pace.

The economy grew at a 2.8 percent annual clip, revised down from 3.5 percent estimated last month, the Commerce Department said. Analysts forecast a 2.9 percent rate.

Reduced inventory "sets up for a better fourth quarter GDP with more restocking," said John Canally, economist at LPL Financial in Boston. "I don't expect a whole of market reaction. There will be more data later today which will be fresher."

November consumer sentiment data and the September Case/Shiller housing price index are also on tap and could provide insight into how firmly a recovery has taken hold.

S&P 500 futures rose 2 points and were modestly below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures were up 3 points, while Nasdaq 100 futures slid 1.25 points.

Hewlett-Packard Co reported a quarterly profit that matched its preliminary results late Monday, and said that while the economy remained challenging, it saw signs of a recovery.

(Additional reporting by Richard Leong; editing by Jeffrey Benkoe)