Pegula arrived in New York in poor form, winning just two matches in her previous four tournaments and losing in the first week of a major four times in six appearances.
While she brushed away the cobwebs with routine wins over Mayar Sharif, Anna Blinkova, Victoria Azarenka and Ann Li, the quarter-finals presented a different challenge.
Pegula has previously struggled at this stage – last year’s run to the US Open final was her first success in the last eight of a Grand Slam singles draw after six defeats.
But Pegula was unruffled by her 1-6 record, capitalising on a slow start from Krejcikova to race into a 3-0 lead, including breaking to love in the second game.
She dominated the baseline exchanges, hitting deep groundstrokes to trap her opponent at the back of the court and regularly attacked the net to keep her opponent off-balance.
Although Krejcikova pulled it back to 4-3, she was left to rue a poor serving performance, with a double fault at 40-30 opening the door for Pegula to break again in the eighth game and then close out the set.
Krejcikova’s serving struggles – winning just 28% of points on her second serve in the opener – continued and a pair of double faults at the start of the second set gifted Pegula an early break.
Pegula was not without her own service wobbles, throwing away a double break lead in the sixth game as Krejcikova sniffed another unlikely comeback.
But she maintained her composure and, a seventh double fault of the afternoon from Krejcikova brought up match point – which Pegula seized at the first attempt.
“I think I’ve been playing some really good tennis. I’ve been playing really solid and having good starts,” Pegula said.
“She had a couple of really good returns when I was serving at 4-1 and we all saw what she did against Taylor, so I’m happy that we’re done.”