The two-fight union between junior middleweight titlist Miguel Cotto and Hall of Fame trainer Emanuel Steward is over.

Cotto announced on his website Tuesday that Pedro Luis Diaz of Cuba has replaced Steward and is training him for his rematch against Antonio Margarito on Dec. 3 (HBO PPV) at New York's Madison Square Garden.

"I met Pedro Luis as an amateur several years ago and had the opportunity to share time with him in several international competitions," Cotto said in a statement. "I was instantly amazed as to the vast boxing technique and conditioning knowledge that he transmitted to his fighters. I feel that together with (strength and conditioning coach) Phil (Landman), Pedro Luis is a perfect fit to bring my best potential for my next fight in December and lead me to victory."

Diaz used to work as a trainer for the powerhouse Cuban national team and has worked with fighters such as former world champion Joel Casamayor and three-time Olympic champion Felix Savon.

"It's kind of surprising. Everything had been in place for me to train him," Steward told ESPN.com.

Cotto was trained for most of his career by his uncle, Evangelista Cotto, before a nasty split. He promoted assistant trainer Joe Santiago to helm his corner, which lasted for two fights. After Cotto was knocked out by Manny Pacquiao in the 12th round in November 2009, he hired Steward to train him.

In their first fight together, Cotto (36-2, 29 KOs) moved up to junior middleweight and stopped Yuri Foreman in the ninth round at Yankee Stadium to win a world title, the third weight class in which he won a belt.

Steward was also in Cotto's corner for his first defense on March 12, a 12th-round knockout of former titlist Ricardo Mayorga.

Cotto will be seeking to avenge an 11th-round knockout loss to Margarito in a 2008 welterweight title fight.

"I want to take this opportunity to express my wholehearted gratitude to Emanuel Steward, who I consider a friend and mentor," Cotto said in his statement. "Because of calendar conflicts and other matters, we were unable to work together for this next fight. He is one of the best trainers I have ever met in boxing and I will be forever appreciative for the two fights we worked together. We have both kept the doors open to maybe join forces in the future if the circumstances and timing are adequate.

"Now I will focus on my training camp. I feel happy and thrilled as ever to commence preparing for December. I will be ready and will win the fight for all of (my fans)."

This is the second high-profile fighter to replace Steward in recent weeks. Former light heavyweight titlist Chad Dawson, unwilling to train in Steward's Detroit gym for what would have been their second fight together, replaced him with one of his former trainers, John Scully, as he prepares for his Oct. 15 challenge of champion Bernard Hopkins.

Although Dawson made the switch, he also has spoken highly of Steward in recent interviews and television appearances.

"Naturally, I thought about that," Steward told ESPN.com, when asked about losing two top fighters in such a short period of time. "But each case is an individual case. Dawson wanted to stay closer to home and that was the last thing I was going to deal with. So he got somebody else he was comfortable with. In this case, Miguel wanted to start training already and wanted me there for longer than our unusual five or six weeks together."

Steward said he had planned to go to Cotto's Orlando, Fla., training camp this weekend and that Top Rank, Cotto's promoter, had already purchased his airline ticket.

Steward said he had been in regular touch with Landman to get updates on Cotto's conditioning.

"Phil said to me, 'Give me two weeks to get his body in shape' and then I was going to come in for the regular camp of boxing training. I was going this weekend," Steward said.

Steward said he was surprised by the switch because he had already agreed to train Cotto for the fight and had received a contract from Cotto's attorney, Gabriel Peñagaricano.

Steward said the first sign there was an issue came last Wednesday when he was in New York attending a news conference promoting last Saturday's fight between middleweight Andy Lee -- Steward's fighter -- against Brian Vera, which Lee won on the Sergio Martinez-Darren Barker undercard.

Steward said Peñagaricano texted him during the news conference to tell him he had emailed the contract and needed to have it signed and returned. Steward said he told Peñagaricano that he wanted to have it reviewed by his representative and that he would "deal with it when I get home from Andy's fight on Sunday."

Steward said on Sunday he received another text from Peñagaricano saying that "it was taking too long and that we decided to move on."

"Andy Lee's fight was important and I got the feeling that they just wanted me to drop it and be in camp already," said Steward, who added he had no financial dispute with Cotto. "But you can't just drop it. It was almost like they thought I should just drop everything. They really wanted me in camp two weeks ago. But I never go in that early anyway. Even if Andy hadn't fought last week, I wouldn't have gone there two weeks ago.

"So they move on. Things happen. I don't even worry about it. I got a call from Gaby (on Monday). He called up and said, 'We want to make sure we're still friends, we may want to use you in the future.' I said, 'Fine, talk to you later buddy.' I have no hostility toward these guys."

Top Rank promoter Bob Arum disputed Steward's claim that money was not an issue.

"It was all economic as I understand it," Arum told ESPN.com. "I think Manny clicked with Miguel as a trainer and Miguel liked Emanuel as a trainer and the results were very good. But as I understand it from Gaby, it was that Emanuel was overreaching in his financial demands. If a trainer, according to the fighter, is asking for what the fighter thinks is too much money, it's the fighter's prerogative not to use that trainer. But all things being equal, Manny is the best trainer for Miguel, no question about it."

Although Steward, who still trains Lee and heavyweight champion Wladimir Klitschko, won't be in Cotto's corner Dec. 3 -- or in Dawson's for the fight next week -- he will be ringside serving in his role as HBO's expert analyst for the pay-per-view telecasts. Had he been training the fighters, HBO would have had its "Boxing After Dark" expert commentator, Roy Jones Jr., fill in.

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