"I felt like I was going to be a bit rusty at times. But I played really well today," Kyrgios said.
"It's surprising because I haven't been doing much on the court. I've just been trying to get into a good head space and be ready.
"I was really happy with the level today."
Kyrgios credited his strength and conditioning coach Martin Skinner for helping him become a better athlete.
Skinner joined the Kyrgios camp in late September, and it's a love-hate relationship that is starting to bear fruit.
"I hate it. There's plenty of other things I'd rather do," Kyrgios said of the new fitness regime.
"He drives me. I'm not the easiest person to get along with at times, and I'm not a good listener.
"But I know that he's pretty intelligent in the gym. So I don't question him too much. He's been working me pretty good."
Kyrgios said his injury withdrawal during the third round of the US Open was the wake-up call he needed to improve his fitness and strength.
"That hurt," Kyrgios said.
"I was doing absolutely nothing at that stage, and it caught up with me.
"I've got to start doing at least the bare minimum, or more, to stay healthy. That's my main goal - to stay healthy this year."I've never really had a good strength and conditioner in my team. I think that was one area where I could develop and I had a lot of potential to take my game to the next level."
Kyrgios' win over Lopez gave Australia a 1-0 lead in the tie ahead of Daria Gavrilova's clash with world No.66 Lara Arruabarrena.
Kyrgios' serve was white hot in the first set.
At one point, the world No.13 served three aces in a row, one of which was clocked at 223km/h.
Kyrgios' 2016 campaign ended in disgrace when he was banned from the ATP tour and ordered to undergo counselling after tanking several points during a match at the Shanghai Masters.
The talented right-hander said the counselling had helped, and he hopes to channel his emotions better in the future.
