Halep smashed a racket on the hard court at Sobeys Stadium after she missed a return late in the third set.
“The fire is back,” Halep said. “It’s a good sign if I do that. It looks like I’m fighting. It helps me sometimes. I don’t know if it’s always good or not, but it helps me.”
The 15th-seeded Halep won the tournament in Montreal in 2016 and 2018. Pegula was seeded seventh.