"I think he's doing a great job. I'm really proud of him," said Lopez on American Idol host Ryan Seacrest's Wednesday morning KIIS-FM radio show. "I've met him and hung out with him a few times. He's a great guy -- really respectful, really cool. I'm glad Karina got him as a partner."
Lopez was addressing a rumor that surfaced last week that while attending the Mercedes-Benz Oscar viewing party at Los Angeles' Four Seasons hotel in February, Smirnoff and Mario were spotted "making out by the valet with their hands all over each other."
Smirnoff subsequently stated she and Mario have a "professional relationship," which he reiterated when he also appeared as a guest on Seacrest's radio show at the same time as Lopez.
"It's a very professional relationship we have," said Mario. "We're just doing the show, and that's it."
Mario said he and Lopez met before filming for Dancing with the Stars sixth-season even commenced when he was rehearsing with Smirnoff.
"We kicked it. [Lopez is] a cool guy," said Mario. "We like some of the same things. I like boxing, he likes boxing. So we're cool. We kick it. There's a respect there."
"Last season I felt bad because they hooked up Karina with Floyd Mayweather, the boxer," explained Lopez. "As you know, I'm a big fight fan. He turned out to be a handful, and let's just leave it at that. So Mario's a big 180-degree turn."
When Seacrest persisted and asked Lopez what he meant about Mayweather, Lopez answered he was just "busy being Mayweather."
Mario said he was apprehensive when first approached about appearing on Dancing with the Stars and it was actually Lopez' third-season participation that inspired him.
"When I saw Mario Lopez on the show -- people I look up to -- it's just like, 'Wow!' I'm looking at them in a different light now," explained Mario. "It's very vulnerable, but at the same time they dance great and they have fun out there. Why not give that to my fans?"
Despite being one of Dancing with the Stars' youngest contestants ever, Mario said the show's judges aren't "having any mercy" on him.
"I got my lowest score this week, which was the weirdest thing because I didn't feel like I did bad," he said. "I don't take it personally. I think it was constructive criticism and honestly I'm inspired to come back and be even better next week."
Mario added he's "never had any formal" dance training but has found his Dancing with the Stars experience "a lot more fun than I thought it was going to be."
"Karina's a great partner. She loves to have a lot of fun and she has a great personality, so that helps," he said. "But there are times in rehearsal when I get really, really stressed out about making sure the steps are right, making sure I remember everything."
Mario explained that since he and Karina "respect each other's passions" they make good partners, a sentiment Lopez agreed with.
"I think they're going to go all the way and do great and be there at the end," said Lopez.