Walker is already scheduled to fight on a Dec. 4 Strikeforce event, and the promotion is currently working on finding him an opponent.
"I was very honored to fight Greg, but Greg was like myself: he was green, he was young," Walker told Ariel Helwani on the most recent edition of The MMA Hour. "I said, 'This time, I've got to fight someone with a lot of experience.'
"I've got to fight a guy with a little bit more experience, that people recognize as an MMA fighter," he continued.
Walker hopes to have his opponent finalized within a week, saying he thinks it would only be fair for his opponent to have the same preparation time as him.
Walker, who stopped Nagy in a third-round TKO in their January fight, said he will again compete as a heavyweight. Still training with San Jose, California-based American Kickboxing Academy, Walker takes regular lumps sparring with AKA fighters Cain Velasquez, Jon Fitch and others.
At 48 years old, he says he realizes he'll never be the No. 1 man in his division, but rather sees MMA as a personal test.
"There's no doubt I'm never going to be a world champion," said Walker, who is featured in the current ESPN The Magazine's "Body" edition. "It's sort of late in my career to try to do that, but what I can be is the best Herschel Walker. And I think the best Herschel Walker is a darn good fighter."
While he was blunt about his own championship prospects, he predicted his teammate Velasquez would capture the UFC heavyweight belt from Lesnar when they meet on Oct. 23, suggesting a first-round knockout. Walker said he has great respect for Lesnar, who he suggested to UFC President Dana White would one day be the heavyweight champ before he even signed with the promotion.
"Cain is a different, different athlete, though," he said. "People think he's a small heavyweight, but he can fight."
Walker said that he and White still get along fine, even though the UFC president blasted Strikeforce when they initially signed Walker.
"Dana and I, we're very nice to each other," Walker said. "We speak, we say hello. He's not talking any smack. He may talk more smack later."
As he did in his first fight, Walker said he would donate his purse to charity, though he joked it was a mistake to do it the first time around.
"Now I got every church in America writing me for this purse right here," he said with a smile.
But hinting at his altruistic nature, Walker spoke about the possibility of helping to build a fighters' union at some point in the future to help deal with the medical costs some fighters incur.
"I think they should have it," he said. "It's very tough right now but if some of the guys come together, they can do it. There's got to be special rules set up, that you become part of the union when you have a certain amount of fights. Some fighters are one and done.
"Take just a small percentage of their purse and put it towards the union," he continued. "Then the league will have to give up a percentage of whatever so they can get insurance for the guys."
Content with his role in Strikeforce and as an ambassador for the sport, Walker said he has no idea whether he'll only fight one more time or continue well into the future. But he made one thing clear, and that was his loyalty to the promotion that gave him an opportunity to compete.
"I would die with them, and that's what I do. People don't understand that but that's the way I am," he said. "If they sink, I'll sink with them because if they give me an opportunity, I'm going to do whatever I can to help them."
Watch Monday's episode of The MMA Hour below.