In sweltering heat, the British No. 1 (pictured) got off to a horrendous start against qualifier Evgeniya Rodina, losing the first four games inside 15min. to the Russian world No. 96 as the Sarnian produced a string of unforced errors and the set ran away from her.
She responded strongly in the second, though, inflicting an early break which set the tone.
Watson then forged into a 5-2 lead in the third before Rodina hit back to win three games in a row to level the decider.
But the Sarnian was not to be denied and came through 3-6, 6-1, 7-5 in 2hr 23min. of energy-sapping tennis.
'I think both of us were feeling the same, it was just who could stick it out mentally and fight through the conditions,' Watson said.
