Shares of Garmin tumbled on Wednesday making it TheStreet's Move of the Day. The company known for its car navigation systems took a hit after Pacific Crest downgraded the stock to 'Underperform' and put a price target in the mid-$40s range. Pacific Crest analyst Brad Erickson said Apple's new iPhone and the possibility of its release of an iWatch could be negative for Garmin. He noted that the rumored iPhone's larger screen combined with its turn-by-turn navigation capabilities could rival the Garmin devices. Shares dumped 4.6 percent to $57.86 on Tuesday, making it the worst performer in the S&P 500.