Watson has made big changes since her first round loss to Madison Keys at Wimbledon, parting from long-time coach Mauricio Hadad and bringing on board former British No 1 Jeremy Bates to help her mould her tactics and adopt a more aggressive game style.
There have been a few encouraging signs too, notably last week in Cincinnati when she recovered from losing the first set heavily to beat former French Open champion Francesca Schiavone.
There was concern when Watson then retired from her first match in New Haven because of a sore hip, which may have been caused by her overcompensating for a niggling elbow problem.
"He knows what he's talking about, especially when it's coming in and volleying," said Watson of Bates. "He's such a nice guy and we get along really, really well."
And the Guernsey girl is confident the hip is no longer an issue, saying: "I've been training the last few days, it's been really good, I haven't felt it at all and I'm just taking care of my elbow."
Making the second round in New York will certainly not be easy, with 21st seed Halep one of the form players of the tour.
She has won four of her last seven tournaments, including in New Haven on Saturday, where she beat Caroline Wozniacki and Petra Kvitova back-to-back.
"I've got a really tough first round, she's had the best year of her career," added Watson.
"But it's a grand slam and no matches are easy. I see every draw you get in a slam as a good draw."
