Ray Beltran stops Takahiro Ao in Round 2 of truTV's boxing debut

Ray Beltran celebrates his win over Takahiro Ao. (Isaac Brekken, AP)

LAS VEGAS - Ray Beltran certainly didn't envision it this way.

Best known for being Manny Pacquiao's sparring partner for many years, the lightweight contender was seeking his first world title Friday but failed in his third attempt.

No, Beltran didn't lose to Takahiro Ao - he actually dropped the Japan-based fighter and then stopped him in Round 2 of the debut of Top Rank's truTV boxing series at The Cosmopolitan.

It was Beltran's battle with the scales that cost him - he came in just 0.4 pounds over the 135-pound limit Thursday - and made him ineligible to win the vacant WBO lightweight title.

However, Beltran elected to focus on the positive and knows there's big things ahead.

"It was a super big win for my career," said Beltran (30-7-1, 18 KOs). "Going into the ring I didn't feel right because of the weight loss yesterday. I didn't feel right in my legs. I knew what I was getting into, I was fighting a two-time world champion, I knew he was a very tough opponent.

"But I caught him with a really good, hard overhand right and I finished him with hard combinations. I can't remember the last time I had a knockout like this."

Ao (27-4-1, 12 KOs) was never right after the knockdown (he barely beat the count) and was unable to keep Beltran off him until Tony Weeks stepped in and halted the bout at 1:29 of the round.

Beltran's first try at a world title came in September 2013 and also ended in disappointing fashion. He beat Ricky Burns in the eyes of most but was unable to win the decision in the champ's native Scotland and settled for a draw. Beltran's eye-catching performance led to a shot against Terence Crawford in November 2014, but he dropped a wide decision.

However, with a performance like he turned in Friday, another world title shot could be just around the corner.