Barcelona's Argentinian striker Lionel Messi (L) celebrates with Barcelona's Spanish midfielder Andres Iniesta (R) after scoring their first goal during the first leg of the UEFA Champions League round of 16 football match between Chelsea and Barcelona at Stamford Bridge stadium in London on February 20, 2018. Pic/AFP

Chelsea manager Antonio Conte rued one costly mistake as Lionel Messi gave Barcelona the upper hand from the first leg of their Champions League last-16 tie by salvaging a 1-1 draw at Stamford Bridge.