District boxer Dusty Hernandez-Harrison is just 19 years old and about to begin his first year at the University of District of Columbia, so the undefeated welterweight’s handlers are taking a measured approach to a promising career.

Hernandez-Harrison, meanwhile, continues to make quick work of opponents during his ascent to contender status. The latest victim was journeyman Guillermo Valdes, 20 years older and yielding a considerable reach disadvantage. He provided little resistance Friday night at Dover Downs Casino & Resort’s Rollins Center.

The deciding sequence came in the last minute of Round 4 when Hernandez-Harrison moved Valdes into the ropes and unleashed a flurry that included a clean shot to the jaw. The blow tilted Valdes’s neck backward, compelling referee Bill Clancy to end the proceedings at 45 seconds.

“I feel great because I did exactly what I wanted,” Hernandez-Harrison said. “I wanted to put pressure but strategic pressure, not too much where I started to look sloppy. I might have at times looked a little sloppy with my punches, but overall I’m satisfied with how it came out.”

Hernandez-Harrison (17-0, 10 knockouts) collected his second knockout over his past three fights, much to the delight of many in the sold-out crowd who made the trip from the D.C. area. So in demand were tickets at the 1,600-seat venue that a promoter purchased a handful outside the hotel in order to provide them to Hernandez-Harrison supporters.

Also among Hernandez-Harrison’s advocates was unified super middleweight champion Andre Ward. Considered perhaps the most accomplished pound-for-pound fighter in the world other than Floyd Mayweather, Ward called Hernandez-Harrison several hours before the bout to wish him luck.

Good fortune, though, had nothing to do with how the Southeast native commanded the ring against Valdes (12-5), who was on his heels throughout his first fight in more than two years.

Following the opening round in which he was landing regularly and authoritatively, Hernandez-Harrison stalked Valdes into the ropes by connecting on a three-punch combination. Soon thereafter, an unimpeded left cross sent Valdes tumbling to the mat only to be saved by the bell.

“I was absolutely shocked that the guy got up,” said Hernandez-Harrison’s trainer and father, Buddy Harrison. “That was a hard left hook. I ain’t seen nothing like that. But I’m glad he got up. We needed as many rounds as we can get.”

It’s been a busy year for Hernandez-Harrison, who has fought six times, all scheduled six-rounders. Hernandez-Harrison has ended half of those fights early, including his last fight in the District on May 18 when he scored a fifth-round technical knockout against Eddie Soto at UDC Physical Activities Center.

The ovation as he walked to the ring to Guns N’ Roses’ “Welcome to the Jungle” provided the prelude for what was essentially a hometown fight for Hernandez-Harrison, who has fought in Delaware three times. The past two of those fights have taken place at Dover Downs.

“I love them coming up here,” Hernandez-Harrison said of his boisterous fan base. “If I can get this many people here, I can’t imagine what it’s like coming back to D.C. again. I remember how May 18 was, and I can’t wait until the next time.”