By the time he suffered the second of back-to-back defeats, Jason Sosa expected to be written off as a former titlist who'd seen better days.

It didn't matter that most experts had the former 130-pound titlist beating Yuriorkis Gamboa on a Nov. 2015 night where he was instead handed a majority decision defeat. The fact that no longer bore the resemblance of major threat in the division was enough to dismiss him as an afterthought.

Little did they know that he was still finding himself as a pro boxer.

"I've been used to nobody giving me  a chance," Sosa (23-3-4, 16KOs) told "I won a world championship when I wasn't supposed to. I take on the best fighter in the world (Vasiliy Lomachenko) and get criticized for losing that. I lose a fight (with Gamboa) that everyone knows I won, but that's supposed to be the end of me.

"Really, it was a wakeup call that I still have more to learn. I only had three amateur fights, most of my pro career was learning (on) the job. I really believe I'm hitting my prime right now."

That theory will be put to the test this weekend, when the 31-year old fighting pride of Camden, New Jersey faces Mexico's Miguel Berchelt (36-1, 32KOs).

The two collide for Berchelt's 130-pound title this Saturday, live from Dignity Health Sports Park in Carson, California (ESPN. 10:30pm ET/7:30pm PT). Berchelt enters with near worldwide recognition as the top junior lightweight in the world, making the sixth defense of the title he claimed in an 11th round knockout win over Francisco Vargas in Jan. 2017.

Sosa was in the process of vacating his secondary title at the time, a necessary move in order to pursue a lucrative showdown versus Lomachenko. It wasn't the way he hoped to end a title run that began with a thrilling knockout win over Javier Fortuna in their June 2016 clash in China, yet a decision he won't ever regret.

"I've always looked for the fights that would prove I'm the best," notes Sosa, who also fought then unbeaten Nicholas Walters to a disputed 12-round draw in Dec. 2015 prior to his first title win. "That's why I wanted to get this fight with Berchelt. I believe he's the best and the (World Boxing Council) title he holds is the most presitigious.

"Really, we've been looking at this fight ever since I was champ and he was a contender.  I got caught zoning out and missed it, but it's coming at the right time."

Sosa carries a three-fight win streak into the ring, including a 7th round knockout of Haskell Lydell Rhodes this past August in the same Philadelphia (Pennsylvania) market where he's spent most of his career. His run might not rival that of Berchelt - who enters on the heels of a repeat knockout win over Vargas in May - but it's good enough to have mentally brought him back to where he needs to be - in position to once again prove the critics wrong.

"This fight is in California, he'll have the crowd and it's Puerto Rico versus Mexico, the best rivalry in boxing," notes Sosa. "All those things motivate me, I can't wait to fight in Cali for the first time. I'm looking forward to hearing everyone say I don't have any chance, and what they have to say once I win this world title."

Jake Donovan is a senior writer for Twitter: @JakeNDaBox