"It's just so cool to be starting," said Kelleher, who finished with a match-high eight goals. "I don't go out there and take anything for granted.
"I felt like I've had to go out there and prove myself to be able to start. I know about the rivalry between the schools and it was exciting to be able to get in there and play."
Pasadena Poly, ranked No. 4 in the latest CIF Southern Section Division VI poll, won its sixth match in a row to improve to 14-2, 6-0 in league. Flintridge Prep dropped to 3-3, 1-3.
Kelleher, who had the match's first six goals, had seven first-quarter tallies to help the Panthers pull away early from the Rebels.
"She's so versatile," Pasadena Poly Coach Ryan Katsuyama said. "She's a scoring weapon, plus a defensive stopper.
"Like in so many of our games, we've been able to go to her [for offense]. Today, she gets the first six goals. We were able to take care of business early by getting the ball to the center and creating steals on the outside."
The Panthers extended their lead to 13-0 in the second quarter before Flintridge Prep received a five-meter goal from Kate Woolley to make it 13-1 with 1:27 left in the first half. Pasadena Poly owned a 14-2 halftime advantage.
"We made a few substitutions in the first half to see where different people could play," said Flintridge Prep Coach Ryan Goto, who got two goals apiece from Woolley and Suzanna Tan and one from Erin Dennis. "We have a lot of new faces to the sport and they are catching on quickly.
"We scored more [Friday] against them than we did in our two matches against them last year. We don't have any players who have club experience, but we are improving every match and not giving up."
Pasadena Poly got three goals each from Catherine Finney and Mimi Morrish. Christina McCarthy and Caroline Harvey contributed a pair of goals each for the Panthers, who got one goal apiece from Allison Woo, Hannah Grotzinger and Kelly Burdge.
Flintridge Prep and Pasadena Poly will meet again at 3:30 p.m. Feb. 8 at Pasadena Poly.