ATLANTIC CITY — Heavyweight Seth Mitchell made the jump from prospect to contender in spectacular fashion Saturday night.

The former linebacker for Michigan State University scored the biggest win of his career, notching a third-round TKO over Paulsboro native Chazz Witherspoon on the Bernard Hopkins-Chad Dawson undercard at Boardwalk Hall.

Mitchell (25-0-1, 19 KOs) dropped Witherspoon (30-3, 22 KOs) with a left hook early in the third. After Witherspoon got up, he kept pressing the attack and walloped him with an overhand right that sent him sagging against the ropes with blood trickling from a cut above his left eye.

Referee Randy Neumann started to administer a standing eight-count, then stopped it at 2 minutes, 31 seconds after looking into Witherspoon’s eyes.

“I knew he was coming to fight,” Mitchell said. “To be honest, I was a little nervous before this fight. He has a lot of experience. I know in the heavyweight division, it only takes one shot.”

Witherspoon nearly earned a win in the first round, jolting Mitchell with some strong right crosses and uppercuts that had Mitchell wobbling around the ring. But he couldn’t land a clean, hard punch before the round ended.

Mitchell took command in the second round with a strong body attack.

“I got a little excited after I had him hurting in the first round and never got back to fighting smart. He dealt with adversity great.

“I was fighting a stupid fight after I got him hurt and I was just looking for the KO.”

Also on the undercard local light-heavyweight Lavarn Harvell scored an impressive victory.

The 23-year-old Atlantic City native treated the early-arriving crowd to a one-punch victory over Tony Pietrantonio, of Sharon, Pa.

“I’ve fought at the Hall before, but it was in the ballroom upstairs,” Harvell said.

“It was a pretty special feeling to fight in the main room in front of all those people.”

Harvell (10-0, 5 KOs) registered a third-round knockout that produced a collective gasp from the crowd. He connected with a right cross that landed flush on Pietrantonio’s chin.

Pietrantonio (7-9, 6 KOs), who accepted the fight on just three days’ notice, was unconscious before he hit the floor.

His head bounced off the canvas and he laid motionless under the ropes with both arms outstretched.

Referee David Fields stopped the bout without a count and immediately motioned for ringside medical personnel.

Ringside physician Dr. Dominic Coletta called for a support board, but it wasn’t needed.

Pietrantonio sat up after a few minutes, climbed onto a stool and then eventually left the ring under his own power.

He was taken to AtlantiCare Regional Medical Center, City Campus, as a precaution and was released later Saturday night.

“A lot of people thought I hit him with a left hook, but it was a right hand,” Harvell said. “I felt that punch all the way up my shoulder and back, so I knew he wasn’t getting up.

“I was so excited that I did a little dance for the fans, but that was before I saw how badly he was hurt.”

The knockout was another step in what has been an interesting boxing journey for Harvell.

Harvell was a regular visitor to the Atlantic City Police Athletic League as a teenager but spent most of his time playing basketball on the second floor. One day, he climbed the steps to the third floor and saw Atlantic City bantamweight Qa’id Muhammad training with his father, Abdur Rahim Muhammad.

“I was terrible at basketball,” Harvell said with a laugh. “I never even tried out for the Atlantic City High School team because I didn’t want to embarrass myself. I was watching Qa’id hit the pads and his father came over to me and asked me if I wanted to try. I said ,‘Sure, I’ll try anything once.’ ”

Abdur Rahim Muhammad first noticed Harvell’s facial resemblance to former heavyweight champion Riddick Bowe —Harvell’s nickname is “Baby Bowe” — but also took note of Harvell’s large hands and lean, muscular build.

After a few amateur fights, he made his pro debut in 2008.

Six of his first eight wins were via decision, but he registered his second straight knockout in four weeks on Saturday.

“I was just a baby when I started this,” Harvell said with a laugh. “Now I’m starting to develop some power.”

In other undercard fights, Toronto junior-middleweight Phil Lo Greco (23-0, 12 KOs) pounded out a six-round, unanimous decision over Hector Orozco (5-11), of Minneapolis. Philadelphia middleweight Julian Williams (9-0-1, 4 KOs) gained an eight-round, unanimous decision over Hector Rosario (7-2-2, 5 KOs), of Puerto Rico. Syracuse, N.Y., junior-welterweight Mike Faragon (18-0, 8 KOs) earned an eight-round, unanimous decision over Sergio Rivera (16-10-2, 10 KOs), of Mexico.

Akron, Ohio, junior-middleweight Shawn Porter (19-0, 14 KOs) took a sixth-round TKO over Patrick Thompson (18-18-1, 8 KOs), of Chicago.

Contact David Weinberg:

609-272-7186