PLYMOUTH — Blood oozing from a two-inch gash high over his left eyebrow, Jimmy Manning leaned forward in his chair, lifted his chin and flashed his signature gap-toothed grin at the trainers and well-wishers sitting around him.

“I didn’t want to give up,” he murmured.

Quiet seconds passed.

“Man,” he broke the silence. “That sucked.”

Just 30 minutes earlier, the New Bedford MMA fighter nicknamed “The Tooth” had been the definition of confident heading into his first-ever professional title fight. With the Cage Titans Pro Lightweight belt on the line during Cage Titans 38 at Plymouth Memorial Hall late Saturday night — technically, early Sunday morning — Manning (5-0) was at the pinnacle of his six-year sojourn into professional fighting, and he entered the hexagon with a steely determination against Dan Dubuque (5-2).

That simmering resolve was tested early by Dubuque — ranked one spot behind Manning (10th) among New England lightweights by Tapology.com — who rode one momentum-shifting shot to a 4:33 first-round TKO of Manning, who suffered his first professional loss.

“It feels awesome,” Dubuque said. “Everyone knows I usually have long fights. Jimmy’s a great fighter. He’s a beast. Hat’s off to Jimmy. I caught him early. He was throwing big punches. If he caught me, it would have been another story.”

For most of the night, Manning had paced silently in a makeshift third-floor dressing room, glancing at the TV screen, occasionally to check on his South Shore Sportfighting teammates. Dressed all in black, only interrupted by the white tape on his knuckles, he spoke of expected victory.

“How long do you think the fight will last?” he’s asked.

“Long enough to dominate,” he answered.

The fight was billed as “perhaps the most talented duo to ever face off in Cage Titans history,” although there might have been a healthy dollop of hyperbole used there.

In his first four professional fights, Manning won in the first round. In his fourth, he finally reached a third round. Many expected this title fight to go a full five, but seconds after the opening bell rang, it was apparent neither fighter was going to play patient.

Manning raced across the mat for a glancing right hook and quickly followed with a kick to the thigh. Neither did much damage, and soon things evened out for the next 30 seconds when they traded combinations.

“My gameplan in all the fights is to close distance immediately,” Manning said. “But Dan’s a different opponent. I wanted to go in and throw him off. I got in there and made some good contact in the beginning.”

A minute in, the fight was still a draw, but that’s when things went south for Manning. Dubuque charged with a shot to the chest and a kick that Manning dipped to block with his arm. As he started to rise back up, Dubuque caught him square in the jaw, dropping Manning to his knee, as Dubuque quickly fired in another shot before missing with his third.

“Dan caught him with the perfect shot behind the ear,” said Manning’s coach, Bill Mahoney. “I think if that shot didn’t land? Jimmy eventually gets that takedown. MMA isn’t like boxing, it’s like fencing. Boxers have giant pads on their hands and MMA fighters have rock-hard bricks on their hands. ”

Manning recovered, securing Dubuque’s leg and fight back onto his feet. He soon had enough leverage to flip Dubuque onto his back, but he quickly got back to his feet as the two wrapped up.

“Every time I hit him, he just fired right back,” Manning said. “He had a few leg kicks. We went back and forth. I don’t think that fight was going to go five rounds.”

They briefly pulled apart to reset, grappled a bit and generally kept things even until about 2:10 in, when Manning was rising to his feet and Dubuque caught him with a knee to the chin. Manning stumbled backwards and Dubuque pounced, laying out a quick combination that sent Manning staggering away.

Dubuque quickly got control of Manning on the ground and started pummeling blows to the back of his head. Manning flipped to his back and push Dubuque off, but soon he was on his side and Dubuque started leveling blows to the side of his head. Fists turned to elbows as Manning’s off-arm flailed helplessly in the air.

That’s when the blood came.

Dubuque landed a couple more elbows to the head as Manning writhed on his back, frantic to escape and survive to a second round, but there was still two minutes left in Manning’s first professional fight with five-minute rounds.

“When I got hit and I saw my head pouring on the mat, I thought, ‘Oh crap, they’re going to stop it right away,’” he said. “I just got caught, man.”

Manning never recovered, as Dubuque relentlessly decimated his head with elbows and fists. Manning lasted another 90 seconds before succumbing, as many in the crowd questioned the referee’s loose leash.

“I was on borrowed time,” Manning said. “He was the better man tonight.”

Manning’s last loss had been four years to the month earlier, on April 5, 2014, during Cage Titans 18. In between had come seven straight wins — including two at the amateur level — a two-year hiatus away from the sport and a renewed sense of urgency as he reached 41 years of age.

“When I first met him, he was a Jiu Jitsu guy with a couple of amateur fights,” Mahoney said. “I think I was kind of betting against him in his first two pro fights. But this time was the first time I felt truly confident, and looks what happens.”

So what about those threats to walk away? Even the official program read “Saturday marks the true end of the line for Jimmy Manning.”

“Let me think about it,” he said before pausing. After a second, he repeated himself.

“Let me think about it.”

Follow Brendan Kurie on Twitter @BrendanKurieSCT