Watson is 145 in the women's rankingsHeather Watson won her first-round match at the WTA tournament in Austin, Texas as she beat Danka Kovinic 7-6 (7-2) 6-4.
The Briton recovered from an early break in the opener and then took a 4-2 lead before Kovinic levelled at 4-4.
Watson failed to take two set points on her rival's serve in the 12th game but won the tie-break to take the opener.
She then kept Kovinic at arm's length in the second set and took her second match point when serving for victory.
Watson will play Sloane Stephens or Taylor Townsend in the next round.
