Like, literally, he wasn't ready. He was stark naked, lying on the floor of his hotel bathroom.
"I had just got done making 136 pounds for my [original] fight," Soto said. "My team told me, 'Dude, the UFC is trying to call you. Better answer before you get cut.'
"The matchmakers said they wanted me to go down to the lobby, that it was an emergency. I run downstairs and they said, 'Barao is injured, you want to take the fight? You want to fight Dillashaw?' I said, 'Yeah, I'll fight him.'"
Soto (15-2) was already scheduled to fight Anthony Birchak in the second fight of UFC 177, which takes place on Saturday at Sleep Train Arena. He was one of only two 135-pound fighters scheduled to appear on the card other than the main event -- in other words, he was right place, right time.
Hours before the official UFC 177 weigh-in, Barao (32-2) fainted while attempting to cut to 135 pounds. The Brazilian was immediately taken to the hospital and withdrew from the title fight.
Soto agreed to step in without hesitation, prompting a wave of "Who is Joe Soto?" pieces and posts on websites and social media.
The 27-year-old has accumulated a solid resume since his professional debut in 2006. He won the inaugural Bellator MMA featherweight title in 2009, but surrendered it in his first attempted defense to Joe Warren in September 2010.
A former All-American NJCAA collegiate wrestler, Soto is currently on a six-fight win streak and has finished 13 of his 15 career wins.
"It's still surreal a little bit, but I'm a professional," Soto said. "I've been doing this for a long time -- 17 fights, a lot of title fights. I've been in this position before.
"Not this crazy of a position, but this position. When I first got to Bellator, they didn't think I was going to win a title and I did. So, I've won titles where I was not expected to win. Nothing this crazy, though. This never happens."
UFC president Dana White said replacing Barao with Soto was a relatively easy call, even though the former Bellator and Tachi Palace Fights champion has never fought in the UFC before.
"He was the guy with the most experience, he has a great record and he has held a title before," White said. "He was the right guy for the job."
According to Dillashaw (10-2), the two have trained with each other previously, as recently as six weeks ago. Soto fought Terrion Ware at a TPF event on Aug. 7 and attended pro practice at Dillashaw's Team Alpha Male several times in preparation.
Duane Ludwig, Dillashaw's head coach, said he had seen Soto fight before and was in the process of breaking his style down.
"I watched his fight with Joe Warren," Ludwig said. "It's a completely different fight [than Barao], but nobody can beat TJ. His style, timing, accuracy power, thought process -- nobody can beat him right now, period."
That will be the consensus thought heading into Saturday's main event, but if Soto is looking for inspiration, he needs to look no further than across the cage. Dillashaw dominated Barao three months ago in a title fight at UFC 173 in Las Vegas, despite being an overwhelming underdog.
The upset was so significant, the UFC's marketing team employed the slogan, "Never Trust the Odds" ahead of the Barao, Dillashaw rematch. That slogan still applies with Soto.
"Greatness is right there," Soto said. "It's mental. You just have to believe. Look at Dillashaw. He beat Barao. Nobody thought he was going to win, so, don't trust the odds."