Boulter has fought her way up the rankings after a strong 18 months in which she stayed fit and caused problems for her opponents with her powerful game.
Now she wants to break a new record and reach the second week of a Grand Slam tournament for the first time.
But coming into the US Open, Boulter admitted that her participation in the Paris Olympics, which were played on clay, left her not as prepared for the hard courts as she could have been.
This experience resulted in her playing only three full matches on hard courts before the start of her campaign at Flushing Meadows.
In contrast, Sasnovich was in top form and had survived the qualification without losing a set.
The difference was evident in the opening set, where Boulter struggled with her first serve and suffered three breaks, undoing the good work she had done to fend off Sasnovich’s unorthodox serve twice.
The Belarusian’s striking move, in which she poses like a flamenco dancer with her serving arm raised before throwing the ball, appears clumsy and lacks wildness.
Boulter managed to break four times, which, together with greater solidity in her service games, allowed the Briton to march confidently through the next two sets.
“It’s not easy to come here and play the first round against someone who was once in the top 30 – she knows how to play tennis,” Boulter, who reached the third round last year, told Sky Sports.
“I knew it was going to be a fight, she played three games on these courts.
“I’m super proud that I managed to stay there and bring a good level to the pitch.”
