Top analyst downgrades Wendy's on slowing sales

A Wendy's classic double cheeseburger and french fries.
Luke Sharrett | Bloomberg | Getty Images

One of Wall Street's top analysts downgraded his rating on Wendy's to sector perform from outperform on the prospect of slowing sales at the burger chain.

"We estimate that Wendy's SSS growth has slowed over the last month, which is concerning given tougher comparisons ahead and low visibility into future marketing," RBC Capital's David Palmer said in a note to clients Tuesday.

Palmer's picks have a 9.7 percent one-year average return with a 69 percent success rate, according to analyst ranking service TipRanks, placing him in the top 4 percent of all Wall Street analysts covering any industry.