Sarmiento switch for Sergio Martinez

Middleweight champion Sergio Martinez will be without trainer Gabriel Sarmiento in his corner when he defends the title against junior middleweight titlist Sergiy Dzinziruk.

The news was disclosed at Thursday's final news conference ahead of the fight Saturday (HBO, 10:30 p.m. ET) at MGM Grand Arena at the Foxwoods resort in Mashantucket, Conn.

"Gabriel won't be in the corner because of some personal issues," promoter Lou DiBella said, although he would not say what the particular reasons were. "It's private, so there's not much I can say about it. But Gabriel was with Sergio in training camp all the way, so they have worked on everything together."

Taking over as the head of Martinez's corner is Pablo Sarmiento, Gabriel's brother. Pablo Sarmiento is a regular member of Martinez's training staff and has worked in his corner for several past fights, DiBella said.

"Gabriel was with Sergio through the close of camp [last] Friday," DiBella said. "We knew about this, but we didn't feel the need to announce it until we had to. We are comfortable with Pablo. This is not an excuse no matter happens in the fight, and we know this is a very tough fight. Sergio said it will make no difference and that he had the best training camp he has ever had. Both of the Sarmientos were there in camp."

Said Martinez, the consensus fighter of the year for 2010: "Pablo is from the same school [as Gabriel], so this will be OK. It's nothing that is a surprise. I am well-trained and ready."

Gabriel Sarmiento helped guide Martinez to the middleweight championship last April, when he outpointed Kelly Pavlik, and then defended the title for the first time with a brutal second-round knockout of Paul Williams in their November rematch. Sarmiento was widely credited with the strategy that helped Martinez, 36, score what was widely acclaimed as the knockout of the year against Williams.

Dzinziruk (37-0, 23 KOs), 35, of Ukraine, defended his junior middleweight title six times and is moving up in weight for the shot against Martinez.

Martinez (46-2-2, 25 KOs), of Argentina but living in Oxnard, Calif., will be making his second title defense.

Coincidentally, the two fighters in the televised co-feature, middleweights Andy Lee (24-1, 18 KOs) and Craig McEwan, also will be without their chief trainers because of conflicts with other commitments.

Lee is trained by Emanuel Steward, but Steward will be manning the corner of junior middleweight titlist Miguel Cotto in his defense against Ricardo Mayorga Saturday night in Las Vegas.

McEwan (19-0, 10 KOs) is trained by Freddie Roach, but he also was unable to make it for the fight because he left a few days ago for the Philippines, where he is training Manny Pacquiao, who defends his welterweight title against Shane Mosley on May 7.

Dan Rafael is the boxing writer for ESPN.com. Follow him on Twitter.