Starbucks Corp SBUX.O fell 2.4% after RBC downgraded the specialty coffee retailer's stock to "sector perform" from "outperform" on valuation and margin outlook. By Devik Jain Jan 7 (Reuters) - Wall Street's main indexes were set to slip at the open on Friday after data pointed to weaker-than-expected job growth, while a rise in wages fueled concerns about higher inflation. The data comes after the minutes from the Federal Reserve's December meeting signaled the central bank may have to raise interest rates sooner than expected amid a "very tight" job market and unabated inflation.