Cisco Systems Inc. shares logged their worst day in more than a decade Thursday, as analysts voiced concerns that China’s COVID shutdown compounded supply-chain problems for the tech giant that smaller rivals managed to mitigate. Cisco CSCO, -13.73% shares closed down 13.7% at $41.72 for their worst single-day percentage decline since Feb. 10, 2011, when shares dropped 14.2% on Wall Street concerns about higher competition and lower margins at the company. The last time Cisco stock closed at its current level was Nov. 23, 2020, when shares finished at $41.64, according to FactSet data. The tech bellwether’s top executives blamed...