Seth Mitchell (right) beat Johnathon Banks by a unanimous decision at Barclays Center in Brooklyn on Saturday night. (Al Bello/GETTY IMAGES)

Seth Mitchell completed his bid to avenge the only loss of his career and at least partially restore his standing in the heavyweight division Saturday night when the Brandywine fighter scored a unanimous 12-round decision over Johnathon Banks at Brooklyn’s Barclays Center.

In a bout that routinely drew boos for long stretches of tedium, Mitchell thrust both arms high as the final bell sounded, sure he had gained redemption from his loss to Banks via second-round knockout Nov. 17.

The judges’ scorecards shortly thereafter confirmed as much — he won by margins of 117-109, 115-112 and 114-112. Mitchell was rewarded for a match in which his attention to defense and caution in his punch selection were largely the difference in the longest fight of his career. Before Saturday, Mitchell's longest fight lasted eight rounds.

Mitchell (26-1-1, 19 knockouts) also reclaimed the North American Boxing Organization and World Boxing Council International belts he had relinquished to Banks in their initial meeting and reestablished himself as contender for a unification title shot perhaps in the near future.

“I felt confident that Banks was looking to counterpunch only,” Mitchell said. “I wanted to be smart and stick to my game plan and be disciplined. I felt I won eight out of 12 rounds and at worst seven out of 12. He hurt me in the [third] round, but I recovered.”

As he promised in the buildup to the rematch, Mitchell focused on defense, and it carried him in the early going. The tactic slowed the pace considerably in the opening round, and fans acknowledged as much by booing multiple times as the fighters measured one another.

But Mitchell brought the crowd to its feet in Round 2 with a right upper cut followed by quick strike to the side of Banks’s head. The combination sent Banks (29-2-1, 19 KOs) to the mat, and Mitchell continued to attack.

In the third, Banks retaliated with ferocity, trapping Mitchell along the ropes and connecting with one shot after the next. It was all Mitchell could do to remain upright as his legs wobbled, but the bell saved him from a premature ending.

Mitchell collected himself over the next three rounds by exercising patience and staying busy. By sheer volume alone, Mitchell was the better fighter over that stretch, while Banks was barely throwing, much less landing.

Mitchell was fighting for the first time in seven months. He originally was scheduled to face Banks in a rematch Feb. 16 in Atlantic City as the co-headliner to Adrien Broner’s first lightweight title defense against Gavin Rees, but Banks had to withdraw when he injured his thumb.

While the sides negotiated another date, Mitchell continued to train with an eye toward reclaiming his place among the most promising American heavyweights. He had ascended to that level thanks to a punishing run through the division that included 10 consecutive victories by knockout, with only one of those fights lasting beyond the third round.

Mitchell reaped the benefits of one his most exhaustive training camps.

“To win this fight I used patience, and I was ready to go the full 12,” Mitchell said. “But with my stamina, I could have gone 15.”