Andre Berto reboots against Jan Zaveck

Saturday, Andre Berto will return from his first defeat to take on a top welterweight in Jan Zaveck. Ed Mulholland/Fightwireimages.com

Andre Berto was stunned. He had just engaged Victor Ortiz in a potential fight of the year, scoring two knockdowns but hitting the deck twice himself in a blistering fight.

When the scores were announced, Berto had lost a unanimous decision and his welterweight title in what was widely viewed as a major upset.

That was April 16. Now, here we are five months later. Ortiz has landed a dream fight with Floyd Mayweather Jr., while Berto will try to regroup after what he calls the worst night of his career. He will challenge titlist Jan Zaveck, a talented fighter from Slovenia with zero name recognition in the United States, in the main event of a "Boxing After Dark" card Saturday (HBO, 10:30 p.m. ET/PT) at the Beau Rivage Resort and Casino in Biloxi, Miss.

But it took the 27-year-old Berto (27-1, 21 KOs) some time to come to grips with the defeat and find the hunger to resume training.

"It was devastating to me," Berto said of the Ortiz loss. "Basically, I just didn't want anybody around me. I didn't want to talk to anybody, so I took a trip out of the country. I just didn't want to be around people. I just wanted to spend a lot of time with myself. It's not in my nature to feel like I got defeated. I didn't feel like I was there [against Ortiz]. I just wasn't physically there."

How depressed, dejected and utterly bummed out was Berto about the loss? After making accusations on Twitter that he thought Ortiz was using performance-enhancing drugs -- which he has since backed away from -- he essentially fled from society.

Berto, from Winter Haven, Fla., went just about as far away as he possibly could, traveling to Indonesia by himself just to get away.

"I just wanted to go get some time for myself," he said. "I went out to Indonesia for a few weeks just to relax. I just wanted to take some time off. Indonesia was a place that I always wanted to go. I just wanted to go relax and to clear my mind. When I got back, I thought I'd be ready, and that's exactly what it was."

Lou DiBella, who has promoted Berto his entire career, said he thought Berto's desire to be alone after the loss was good for him. He wasn't worried, as some others were.

"I found it refreshing as opposed to a cause for concern," DiBella said. "Andre has all the talent in the world, but he had the most difficult night of his career against Ortiz. Berto didn't walk into the ring like Andre Berto, and that does not take anything away from Ortiz, who is an excellent fighter and won the fight. But I've been with Berto since his first fight, and in the locker room before the fight he didn't look like himself. He was not comfortable and Ortiz had the eye of the tiger.

"So I thought it was good to go and think on his own. He's a big social media guy, and if you noticed, there was a decrease in his activity. I think he has the eye of the tiger right now. He wants to talk less and tweet less at the moment, and do more."

Berto discovered he had anemia after the fight, which is what he attributes to his lack of energy that night. He also began working with disgraced BALCO founder Victor Conte on his nutrition and supplement program. Conte works with other fighters as well, including super middleweight titlist Andre Ward, bantamweight champion Nonito Donaire and former junior welterweight titlist Zab Judah.

"Beforehand, I didn't really do much of the nutrition aspect," Berto said. "I basically just trained hard in the gym. I didn't do vitamins or protein shakes, and it started to take a toll after a while. We're in there beating up our bodies time and again. After the Ortiz fight, I just looked for a nutritionist who knew what he was doing and who could get my nutrition where it needs to be. ... [Conte] really breaks everything down to what everything is supposed to do and how important it is to your body."

Berto said he had no qualms about working with Conte, despite his past.

"Of course, he has a rough past [because] of some of the things he did, but I know, from being there, everything he's doing [now] is legit," Berto said. "Everybody he's worked with in the past knows everything they were doing was dirty. If someone's sticking a big needle in your ass, you know something is different. I know what I'm doing is legit."

When Berto returned from his self-imposed exile to Indonesia, he said he felt like training again and left it up to his team to line up his next fight.

"When I got back, I felt like I was ready to go," Berto said. "I said to my team, 'Get on the plane, I'm ready to jump into camp, let's go.' You can't get frustrated by it, you can't let it beat you up. This is a sport. I've done what a lot of fighters haven't been able to. Everybody basically watched my career live and in color on HBO. These fans on HBO have seen me down, have seen me lose now. It's just tougher to kind of deal with. It's hard to take, but that's the reality of it. You can't run away from it. This is the reality of it. You have to be able to deal with it."

Now Berto has to deal with Zaveck (31-1, 18 KOs), 35, who will be making his fourth title defense and fighting in the United States for the first time.

"I want to point out something that [Zaveck] tweeted, because I thought it was an excellent comment by a world champion," DiBella said. "What he tweeted was, 'A real champion doesn't hold his title hostage.' That is why he is coming to America, fighting one of the very best fighters in the country and one of the very best welterweights in the world. That is a great tribute to the championship spirit of the champion because, in this day and age, too many champions do hold their titles hostage."

The only Slovenian to ever hold a world title, Zaveck, who last fought in February and knocked out American journeyman Paul Delgado in the fifth round of a lopsided fight, has wanted to come to America to challenge himself for quite some time.

"This is my first fight in the U.S., but I promise that it won't be my last," said Zaveck, who speaks English fairly well. "A win over someone like Berto will elevate me to a whole new level. Just like everyone else, I want to fight Mayweather and [Manny] Pacquiao, and I see this fight as my golden opportunity to make that happen."

The Berto fight is the ideal opportunity for Zaveck to make his American dreams come true. He isn't a guy who has been afraid to go on the road. After all, he went to South Africa in December 2009 and knocked out hometown fighter Isaac Hlatshwayo in the third round to win his belt.

"In boxing, it doesn't matter where you fight -- Africa, America, Asia, Australia, Europe," he said. "For me, the point is, I love boxing. I know when we come into the ring, that does not matter, whether you're in Europe or anywhere in the world."

Bailey awaits winner

Former junior welterweight titlist Randall Bailey (41-7, 36 KOs), who is a mandatory challenger for a welterweight belt, stepped aside to allow Berto to challenge Zaveck.

Before Zaveck and Berto do battle, Bailey will fight Yoryi Estrella (10-5-2, 7 KOs) in a stay-busy fight on the untelevised undercard and is supposed to get first crack at the main event winner.

"I'll be watching the fight very closely Saturday," Bailey said. "It doesn't matter to me who wins because I will be ready for either of them in the next fight. I wish them both luck on Saturday night, because regardless of who wins the belt, they won't own it for much longer."

DiBella, who promotes Bailey and Berto, said he appreciated Bailey stepping aside.

"This fight would not have happened if Randall Bailey didn't allow it to happen," DiBella said. "He was the legitimate mandatory. The reason Bailey let it happen was because he's a smart guy, he's been around the fight game a long time and he understands that he's got to feed his family. He understands that this fight was saleable to HBO because of all of Berto's TV exposure, where his fight against Zaveck would have taken place in Europe and no one [in the U.S.] would have seen it.

"Bailey will make a lot more money as a result of that decision in his next fight. He did the right thing, because these are the two best available welterweights in the world and because it is a fight that HBO is covering. That's why Bailey stepped aside and that's why the fight is happening."

In the televised opener, fast-handed 2008 U.S. Olympian Gary Russell Jr. (17-0, 10 KOs) -- a 23-year-old from Capitol Heights, Md., and one of the top prospects in boxing -- makes his HBO debut against Mexico's Leonilo Miranda (32-3, 30 KOs) in a scheduled eight-rounder.

Dan Rafael is the boxing writer for ESPN.com. Follow him on Twitter @danrafaelespn.