Two-time Olympian Rau'shee Warren knew that with the caliber of boxers in the U.S. Olympic Boxing Trials, particularly in the flyweight division, he would have to have a solid game plan to preserve his dreams of making a third Olympic team.

So, instead of relying solely on his jab in Sunday night's fight against 2011 national flyweight champion John Franklin, Warren used an outside attack. It worked to perfection, as he defeated Franklin 22-13.

"A lot of people like seeing my speed, but I was just trying to keep him (Franklin) off balance," Warren said.

Warren made good use of the outside attack, seemingly getting stronger as the bout progressed.

"Throughout the bout, I was talking to my coach," he said. "I decided to just make it look easy by scoring from outside."

Warren will next face Stephen Young, a 39-13 winner over No. 4 seed Gabriel Montoya, in the winner's bracket.

Meanwhile, another drama was playing out in the welterweight division, as top-seeded Errol Spence of Dallas had his hands full with unseeded Samuel Vazquez. Spence's speed, as well as overhand and straight lefts, proved to be the difference as he defeated Vazquez 24-17.

"I kept my hands busy, but I sometimes dropped them a little bit," Spence said. "The first fight is always the toughest one, and he (Vazquez) didn't do anything he hadn't done before. He took my punches kind of well, and he kept coming."

Spence will face unseeded Bryant Perrella, a 27-21 victor over Houston's Regis Prograis.

A big upset came in the super heavyweight division, as unseeded Brett Rather defeated No. 1 seed Jonathan Hamm 83-81 in a tiebreaker. Rather, despite a huge height disadvantage, effectively worked the inside and landed numerous punches, knocking Hamm into the challengers' bracket.

"It was a reality check for me," Hamm said. "I felt I threw enough punches, but you have to give Rather credit. He kept coming forward, and he deserved to win. Next bout, I know what the judges are looking for. I'm going to let my hands go and throw 100 punches a round."

While most of the seeded boxers in Sunday afternoon's session did well, there were some upsets.

The top two seeds in the middleweight division were defeated. Philadelphia's Jesse Hart, who previously fought as a light heavyweight, dropped down in weight class and beat No. 1 seed Chris Pearson 18-6.

Second-seeded Edgar Alvardo Jr. of San Bernadino, Calif., lost a 20-16 decision to Milwaukee's Luis Arias.

The bantamweight division saw a pair of upsets as well. No. 2 seed Joet Gonzalez of Glendora, Calif., lost to Traimaine Williams of New Haven, Conn., 14-12, while third-seeded Antonio Nieves of Cleveland lost to O'Shanique Foster of Orange, Texas.

The double-elimination tournament continues Monday.