Updated

Julio Cesar Chavez Jr. recovered from a slow start he blamed on leg cramps and stopped Andy Lee at 2:21 of the seventh round Saturday night to retain the WBC middleweight title.

A right uppercut by Chavez snapped Lee's head upwards and sideways and Chavez connected on a barrage of punches before referee Laurence Cole intervened and waved an end to the fight.

"I began by studying him," Chavez said. "I saw he had nothing, and I dove in."

Chavez (46-0-1, 32 KOs) began tentatively, not even throwing his first punch until 75 seconds had elapsed in the first round, and was initially outboxed by Lee (28-2), a much taller challenger than Chavez had previously faced. But as the next two rounds passed, the Mexican champion began to stalk Lee, blasting him with right-cross counterpunches.

"He's strong, he's young, he's big," Chavez said of Lee. "He gave me everything he had, but he couldn't do anything to me."

In the fifth round, Chavez openly taunted Lee's punching power, dropping his gloves, grinning wildly and pretending to have wobbly knees. From there, Chavez's strength put Lee in retreat, and Chavez punished him with left hooks to the body and right uppercuts to his head.

"I couldn't hold him off," Lee said. "He was too big and too strong."

Lee's trainer Emmanuel Steward concurred with his fighter's assessment, saying, "Junior fought a smart fight. He's very strong. He passed the test."

Chavez attributed his initial tentativeness to leg cramps.

"It hadn't happened to me in about three years, last time it happened was in Ciudad Juarez," Chavez said. "I thought I wouldn't last 12 rounds."

With the victory, Chavez put himself in position for a title-unification fight with recognized world middleweight champion Sergio Martinez.

"Martinez moves a lot," Chavez said. "That's a fight I have to make."

Before the main event, El Paso Mayor John Cook, who also performed the National Anthem in the ring, presented promoter Bob Arum with a key to the city, in an expression of gratitude for Arum's decision to both select El Paso as a host city and then to resist an initial cancellation of the event by University of Texas system Chancellor Francisco Cigarroa in April.

The decision that initially cited a "higher than normal" risk assessment was later reversed.

The Sun Bowl was teeming with law enforcement officers Saturday, there to provide beefed-up security, including bag checks and pat-downs at the entrance. Helicopters circled the venue on the University of Texas at El Paso campus.

University spokeswoman Veronique Masterson said earlier in the day the visible security would be similar to other sporting events at the Sun Bowl.

Masterson said of the snipers and helicopters: "we always coordinate with local and other law enforcement agencies. It's normal for a special event like this."

Assertions of El Paso's safety record were ubiquitous, including statements on the blue mat that read "America's Safest City" and a reminder from ring announcers before each of the evening's nine matches.

"Thank you all for standing up to people on the outside," Arum said to cheers from the Sun Bowl Stadium crowd of 13,467. "If you all stand up together, nobody from Austin and nobody from Washington can push you around."