By Miguel Rivera

This past Saturday night at Madison Square Garden in New York City, former four division world champion Miguel Cotto (41-6, 33 KOs) went out on his shield as he dropped a twelve round unanimous decision to Sadam "World Kid" Ali (26-1, 14 KOs), who in the process captured the WBO junior middleweight world championship.

A stunned crowd of 12,391 heard scores of 115-113, 115-113 and 116-112 come down for Ali.

Ali, a 2008 U.S. Olympian from Brooklyn, hurt Cotto twice in the early rounds and used a lot of movement and activity to give Cotto fits in the contest.

The defeat was a big shock as Cotto was an 11-1 favorite and some bookmakers had him listed even higher. He was looking to end his career with a big, but thing did not turn out that way. Cotto had just captured the WBO title back in August, with a twelve round domination of Japanese contender Yoshihiro Kamegai.

During the action, Cotto suffered an injury and that could have opened the door for either a rematch or another return fight in Puerto Rico.

However, the six-time, four-division world champion and the fighting pride of Caguas, Puerto Rico confirmed his retirement after the bout

According to Cotto, he suffered the injury to his left arm in the seventh round. The injury was not revealed until the fight was over, but the issue was clear when looking at Cotto's arm - as his biceps appeared to be rolled back and bruised.

Cotto is now back in Puerto Rico and he will undergo surgery on Wednesday to correct a ruptured biceps tendon, according to Cotto's partner in Promosiones Miguel Cotto, Héctor Soto.

"He has a ruptured tendon of the distal biceps. It is retracted back from 6 to 7 centimeters [on the arm]. He has a large bruise. And that's why there is pain," said Soto.

The doctors who will operate Cotto are Omar Morales and Gerardo Pérez Román, Soto explained