Willock, on loan from Arsenal, scored his side's first goal and has now netted in each of his last four appearances for Newcastle.
The first three of those came from cameos off the bench, and Willock was grateful to get the chance to make an impact from the start against Leicester.
"We knew we had to get something out of today's game," Willock told Sky Sports. "To come here and do it so convincingly is brilliant.
"I've come off the bench a few times and scored. So I was knocking on the door and I told the manager I needed to start and he believed in me and put me in and hopefully I repaid him."
Willock added: "They are a top side, fighting for the Champions League.
"We had to defend well and knew we had more than enough pace on the counter to get the goals like we did today. That was not how we wanted to finish. We wanted to stay on top.'All week we have been trying to stay compact and when we get behind them be ruthless. I am happy Callum [Wilson] is back on the scoresheet and that will give him confidence."