RBC Capital analyst Mark Mahaney downgraded Groupon (GRPN) to Underperform saying the company's Q1 results highlighted "deteriorating fundamentals" and "substantial challenges" going forward.

Growth in North America revenue, gross profit, local billings and units all decelerated in Q1, Mahaney tells investors in a research note. He cut his price target for Groupon shares to $3 from $4. The stock closed Friday down 81c to $3.62.