Shares of FitBit shed more than 11 percent on Thursday, after Pacific Crest downgraded the wearable fitness device maker to "underweight" from "neutral."
The stock saw its worst day since May 5 when it fell 18.83 percent.
Brad Erickson, an analyst for Pacific Crest, said in a note to clients on Wednesday that sales for FitBit's new flagship product, Charge 2, was off to slow initial sales and recommended investors to sell their shares.
FitBit announced the release to major retailers worldwide in a press release on Monday.
Erickson acknowledged that the Charge 2 may ramp up more sales as the holiday season nears, but the rates still lie well below what the Blaze and Alta models had when they were released earlier this year.
FitBit continues to face stiff competition in the wearable devices industry from products like the Apple Watch. Apple just released a new generation of its watch earlier this month with waterproof features.
The stock closed at $14.82 on Thursday and is down nearly 50 percent year to date.