By Keith Idec

Sammy Vasquez called 911.

The Army veteran didn’t know what was wrong one day late last spring at his Colorado home. The welterweight contender just knew that he had never felt something so painful – not when literal bombs exploded near him in Iraq and not when opponents hit him with figurative bombs inside boxing rings.

“I thought maybe something burst, like maybe my appendix or some sh*t,” Vasquez told BoxingScene.com. “I didn’t know what it was. I was just curled up in a ball on the floor, crying, because it was just like the worst pain I ever felt in my life.”

Kidney stones inflicted all that pain. That excruciating condition was the byproduct of another affliction, a tumor on his pituitary gland.

Vasquez underwent surgery a few days later to crush those kidney stones. Unfortunately, this fearless fighter needed another procedure.

The tumor was causing his body to produce too much calcium, and not enough vitamin D. Among other symptoms, it caused the typically energetic boxer to tire easily.

Problem was, Vasquez already had started training camp for an important fight on free TV against former WBA welterweight champion Luis Collazo. If Vasquez were to beat Collazo, he would’ve continued on a fast track toward a world title shot.

Withdrawing from the fight wasn’t an option, according to Vasquez, no matter how his condition affected him. Determined to remain in the fight, Vasquez hid his doctor’s diagnosis from his manager and trainer.

He didn’t tell them he needed surgery until July 16, in the immediate aftermath of Vasquez’s unanimous-decision defeat to Felix Diaz, a late replacement for Collazo because he tore a calf muscle in training camp.

“They were pissed off,” Vasquez said. “They care about me and they wanna see me succeed. They were like, ‘You should’ve told us.’ But at the end of the day, us fighters, man, when your back’s against the wall, you’ve gotta do what you’ve gotta do for your family.

“We just bought a house and all this stuff. Then, all of a sudden, after I bought the house I found out I had this tumor. And I’m like, ‘What the hell am I supposed to do, not fight now? If I don’t fight we could potentially lose this house.’ ”

Vasquez and his wife, Delrae, conferred with his doctor. Putting off the surgery until after his fight meant there was about a 60-percent chance he’d have to deal with kidney stones again, but that was a risk Vasquez was willing to take.

Eight months later, Vasquez wishes he had pulled out of that 10-round fight, which he lost on all three scorecards (96-93, 95-94, 95-94).

“I just put it in my head, like, ‘Hey, I’m gonna fight through this. It’s no big deal. I’ll have the surgery later,’ ” Vasquez said. “And then I ended up getting kidney stones, calcium kidney stones, during the camp. I had to get a stent put in and surgery to blast those out of there.

“And it affected me. I was very fatigued, sleepy and things like that. I wasn’t a hundred percent. Mentally, I fought it myself. I didn’t tell my team about it, or they wouldn’t have had me fight. And I was just thick-headed. I learned my lesson, not to do that anymore.”

Vasquez had surgery to remove the tumor two days after Diaz defeated him. He was able to resume physical activity about a month later.

Several months later, Vasquez again was offered a fight against Collazo.

They’ll meet Thursday night in a 10-round main event at Horseshoe Tunica Casino & Hotel in Robinsonville, Mississippi. Vasquez (21-1, 15 KOs) and Collazo (36-7, 19 KOs) will headline an FS1 telecast set to start at 8 p.m. ET/5 p.m. PT.

The 30-year-old Vasquez views this as his shot at redemption following a poor performance in his loss to Diaz (19-1, 9 KOs), who won a gold medal for the Dominican Republic at the 2008 Summer Olympics in Beijing.

“You’ve gotta deal with losses,” Vasquez said. “That comes in life, just in general. I don’t dwell on losses at all. I’m not somebody that does that. I learn from my mistakes and I move on. I was going through some stuff medically in that fight that was hindering my performance.

“And not to take anything away from Diaz – he’s a great fighter. He was an Olympic gold medalist. He was the best in the world and he’s done very good in his pro career as well. But I know I wasn’t a hundred percent for that fight. I think if I was a hundred percent, I would’ve took him out. But I learned a lot from the fight. I don’t dwell on it. It just helped me improve, to be better for this fight with Collazo, now that I’m a hundred percent.”

The left-handed Vasquez intended to rely heavily on his jab to set up power punches against Diaz, also a southpaw. Instead, a sluggish Vasquez found himself laying on the ropes all too often, a sign that he didn’t have his legs during a fight in which he desperately needed to maneuver his way to victory.

“You could see in the first three rounds, I was good,” Vasquez recalled. “I was boxing him, the jab was on point, things like that. But after that, once he started putting the pressure on, I couldn’t do anything. My legs were giving out on me. I felt like I was in quicksand and I couldn’t do sh*t about it.”

The resilient Vasquez has survived worse than what happened in the ring against Diaz in a fight FOX televised from Birmingham, Alabama. The Monessen, Pennsylvania, native served two tours in Iraq, sought treatment for post-traumatic stress disorder when he came home and then had those two surgeries last year.

Recovered mentally and physically, Vasquez hopes a victory over Collazo can move him back into contention to fight for a world title.

“I think a win would definitely put me back up to the top echelon again,” Vasquez said. “Collazo’s a very aggressive fighter. I mean, we know he likes to bring it. He has a huge resume and to have someone like him on my resume, with a ‘W,’ would be huge. I think it definitely would help me further my career and help me get back in the running to be a world champion.”

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.