The Clippers moved to 7-3 for the season with a 98-88 victory over the defending NBA champions at Staples Center on Monday.
Leonard, the Finals MVP with the Raptors last season, had his worst game since joining the Clippers, as he had a career-high nine turnovers and shot only 2-of-11 from the field.
He was harassed by the Raptors (also now 7-3) throughout, often double-teamed and trapped as well as being challenged at half court.
But Leonard felt the experience proved beneficial and produced some good moments as the game progressed, eventually finishing with a line of 12 points, 11 rebounds and nine assists.
"They made me better," Leonard told reporters. "As soon as I walked across half court, they were trying to get the ball out of my hands, sending an extra defender.
"[Opponents] are going to do it at times in the playoffs and regular season and they [Clippers team-mates] are going to knock down the open shot. That's what wins games: open shots. We came out with the win.
"They did a great job on me - but I'm glad they did. It made me better and it's going to make my team-mates better as well.
"It's even better coming out with a win. My team-mates made shots. It wasn't one of those nights for me."
Leonard acknowledged facing the Raptors is always going to feel a little different given he remains on good terms with head coach Nick Nurse and much of the roster.
But he was keen to leave last season's NBA title and his subsequent free agency decision in the past.
"We grew a relationship," Leonard added. "It's just fun being able to compete against guys you were with last year.
"From that aspect, it's a little bit more competitive because you do talk to them. So I can tell them that we won the game.
"But no, why would I think about last season? It's over now, we won.
"Like I said before, I had a great time here and it's the next chapter. I can't live in the past and be so excited that I won [a championship].
"I won with a different team, a different unit. They want to have that same feeling and I do as well. I'm a Clipper right now and I'm trying to win."