Leclerc damaged his car after colliding with Max Verstappen right at the start of the race, causing the Monegasque driver to fall to the back of the grid and attempt to climb back up the grid at Suzuka.
Sainz spoke to Motorsport.com about coming out on top of a Ferrari in Japan, and said: "Oh yeah it did (feel great). When you have a Ferrari 10 seconds behind, and when they are a couple of seconds faster in race-pace, you think you're not going to make it.
"But I had been saving my tyres at the beginning of the stint and when I was required to push I was able to find half-a-second of pace and although he was half-a-second quicker for the first three or four laps, he suddenly degraded and I kept up the pace and he gave up. It was nice!"
The Spanish driver finished in P5 yet again on Sunday and he continues to impress in his debut season for McLaren, recently overtaking Pierre Gasly, who spent half of the season at Red Bull, into sixth-place in the drivers' standings.