WASHINGTON — Jessie Vargas talked all week about his new-found power. He said that he would show it off against undefeated former Olympian Sadam Ali on Saturday night at the D.C. Armory.

Did he ever. After looking to be a half-step slow in the first few rounds, Vargas flashed his power in the middle rounds of the HBO co-feature, knocking Ali down twice before referee Kenny Chevalier stopped it at 2:09 of the ninth round.

Vargas, a Las Vegas native, takes home the vacant WBO welterweight title he nearly won against Timothy Bradley last June, but lost when the fight was ended prematurely by the referee, who mistook the 10-second warning for the final bell. Vargas had Bradley out on his feet at the time and might have dropped him in the 8-10 seconds he would have had left.

Vargas wants another shot at Bradley, who fights Manny Pacquiao on April 9 in Las Vegas. The belt he won Saturday was the belt Bradley vacated so he could fight Pacquiao instead of Ali, the mandatory.

“Win or lose, I want Bradley,” an elated Vargas told reporters at ringside afterward. “We have some unfinished business.”

Vargas (27-1, 10 KOs) outworked Ali, landing 159 punches overall to 118 for Ali, according to CompuBox statistics. The power punches were much closer, with Vargas landing 95 (45.2%) and Ali 93 (44.9%). The difference was that Vargas’ jab was more effective and efficient (he landed 64 to Ali’s 25).

“I tore him apart piece by piece,” Vargas said. “This is what I’ve been working for all my life.”

Vargas gave all the credit to his new chief trainer, Dewey Cooper, who took over from legendary fighter Erik Morales when Vargas replaced his team after the Bradley loss. He said Cooper worked on his strength throughout training camp.

“I thank Dewey Cooper for the victory,” the 26-year-old Vargas said. “We put together a new team and (he) showed me a new technique to develop more power. It was a move to turn my hips more and drive in the power.

“He brought the best out of me. Jessie Vargas is here to stay, I guarantee that.”

Ali (22-1, 13 KOs) lost for the first time in his professional career. He said he twisted his ankle when he went down because the ring floor was wet with sweat. The crowd booed a bit, thinking it was hearing an excuse from Ali.

“I just got caught with a good overhand right I didn’t see,” Ali said. “(He) really surprised me with that shot. I wasn’t expecting that, but as I went down I twisted my right ankle and after that I wasn’t able to move like I wanted.

“But I stuck it out. I kept coming back. Unfortunately when you’re in pain it is very uncomfortable.”

Ali said he felt really strong before the fight.

“I felt very confident and sometimes that isn’t enough,” he said. “I need to go back to the drawing board and make sure to correct the mistakes that I made in the ring tonight. I’m going to come back better than ever.”

(Photos of Vargas and Ali by Tom Hogan, Hoganphotos)