Stocks futures edge up ahead of payrolls report

Stock index futures were slightly higher in thin trading Friday, after four days of gains on the S&P 500, and ahead of a government payrolls report expected to show a tick up in hiring last month and a slight increase in the unemployment rate.

* Zynga shares fell 20 percent in premarket trading after it slashed its 2012 outlook for a second time, fanning doubts about its ability to halt a steep decline in earnings. Facebook , which derives over a tenth of its revenue from fees paid by Zynga, saw its shares fall 2.6 percent.

* Sprint Nextel is considering making a rival bid for MetroPCS Communications , which agreed Wednesday to a merger with Deutsche Telekom's T-Mobile USA, according to people familiar with the situation.

(Reporting by Rodrigo Campos; Editing by Bernadette Baum)