The capture of the Gulf cartel's kingpin may have crippled the once mighty gang, but its downfall could usher in more violence in Mexico as powerful rivals battle for supremacy, analysts said.
The arrest of Jorge Eduardo Costilla Sanchez, alias "El Coss," on Wednesday allows President Felipe Calderon to cross off the 23rd name from his list of Mexico's 37 most wanted criminals.
The capture came a week after the arrest of another top Gulf leader, Mario Cardenas Guillen, who lost one brother to a gun battle with troops in 2010, while another, former kingpin Osiel Cardenas Guillen, is in a US prison.
"This leaves the group completely leaderless," Guadalupe Correa, an expert on Mexican drug trafficking at the University of Texas at Brownsville, told AFP. "It operated for decades. It has clearly been weakened."
The leadership vacuum within the Gulf cartel offers a golden opportunity for their former enforcers, the Zetas, to position themselves as the dominant force in the northeast region bordering Texas.
The Zetas, founded by former elite soldiers, have fought the Gulf cartel for control of lucrative cocaine and marijuana trafficking routes to the United States ever since the two groups broke ties in 2010.
The feud raised the murder rate in the states of Tamaulipas, Nuevo Leon and Coahuila, which neighbor the United States.
With the Gulf cartel almost out of the way, the Zetas may intensify their battle for national dominance with the Pacific coast's Sinaloa cartel, which is run by fugitive billionaire Joaquin "El Chapo" Guzman.
"This is the beginning of a reconfiguration of organized crime in Mexico, with the strengthening of two important organizations, Sinaloa and the Zetas, and the weakening of the rest," Correa said.
"This means war between the Zetas and the Sinaloa cartel," she added.
Despite their historic rivalry, the Gulf cartel had been negotiating a truce with Sinaloa in order to take on the Zetas together.
The Sinaloa cartel, considered the most powerful group in Mexico, has already made its presence felt in Tamaulipas.
In May, 15 decapitated bodies were found in the border town of Nuevo Laredo with a message directed against the Zetas. A few hours later, nine corpses were found hanging from a bridge, presumably left there by the Zetas.
"The Zetas have risen to be the second most important cartel during the six-year term of Calderon," which ends in December, said Ricardo Ravelo, a journalist who has written several books on Mexico's cartels.
"There will be a lot of violence at the end of the six-year term," he added.
Some 60,000 people have been killed in drug-related violence since 2006, when Calderon deployed 50,000 troops across the country to take on the gangs, according to analysts.
While the government can point to a series of high-profile arrests in the last six years, analysts say the captures have fueled violence because gangs fight to the teeth in order to fill the void.
Mexico counted six cartels when Calderon took office in December 2006. Today there are around 14 syndicates, Ravelo said.
The Zetas themselves are believed to be struggling with internal divisions between its two leaders, Miguel Angel Trevino, "Z-40," and Heriberto Lazcano, or "El Lazca."
"It's a complicated map, which indicates a paradox in the drug war: It did not exterminate any gangs. It had the effect of multiplying them," Ravelo said.