But he's looking forward to stopping the "greatest of all time" talk surrounding Johnson in 2018.
Last year Dillashaw (15-3) campaigned hard to face Johnson in his record-setting 11th flyweight title defense. Ultimately Johnson (27-2) fought Ray Borg instead, whom he submitted in the fifth round. With the win, Johnson broke Anderson Silva's mark of 10 consecutive title defenses.
Dillashaw went on to claim the UFC bantamweight championship in November and is now targeting Johnson in 2018. It's too late for him to spoil Johnson's bid at history, but Dillashaw still sees plenty of appeal in the fight.
"I'm looking to come in and dethrone him from his legacy," Dillashaw told ESPN. "He won't be able to call himself the 'GOAT' anymore.
"It's so easy for him to continue calling himself that and take the fights he thinks are a little easier. He's a cerebral fighter. He and his coach are smart guys, and they know I bring the greatest threat. I think he knows that's going to be a tough one for him to win."
Last month UFC president Dana White said the matchup is "going to happen," but there's been no official update since.
Dillashaw, 31, celebrated the birth of his first son, Bronson, on Dec. 28. He told ESPN he's confident the fight will get signed, but he needs about 16 weeks to cut to 125 pounds.
After fighting once in 2017, he also intends to be more active this year. And of course, his motives in dropping weight go well beyond affecting Johnson's legacy.
Since 2012, Dillashaw has suffered just two losses -- both via split decision -- to Raphael Assuncao and Dominick Cruz. Had those two decisions gone the other way, as he says they should have, Dillashaw would be on a 13-fight win streak and in talks for best pound-for-pound in the world.
He has already avenged the Assuncao loss and intends to do the same against Cruz. The quickest way to right the pound-for-pound rankings though, is to beat Johnson, who's universally ranked No. 1.
"It's frustrating because I believe I should be a lot higher [pound-for-pound ranking]," Dillashaw said. "Couple split-decision losses I felt should have gone my way. That's the way this sport is. I don't lose to Cruz [in 2016], I'm up there for best in the world. It's all meant to be. It's going to end up leading to a great thing."
"That's what I'm hearing from fans and journalists. They believe me fighting Johnson is not only the most-hyped fight for 2018 but the most talented."
Dillashaw, who fights out of Denver and Los Angeles, credited Johnson for holding two victories over his teammate Joseph Benavidez and said the 125-pound division as a whole is "improving," but he also said he hasn't fought a fighter of his caliber in years.
"On average, there aren't those guys who will bring everything in that weight class," Dillashaw said. "They don't have the power, footwork, cardio and wrestling I have. I don't have a gap that Demetrious can take advantage of.
"When you see him manhandle guys and finish fights late in championship rounds -- out-grapple them -- he's not going to be able to do that to me. And I think that's a scary thing to him, that he doesn't have something to fall back on."