By Miguel Rivera

A left shoulder injury could jeopardize the ring return of four division champion Juan Manuel Marquez and the latest issue could even force him into final retirement.

Marquez is currently training to return in July or August after more than three years of inactivity. However, a knee injury prevented him from thinking about returning last year. He was training without any problems, but now the shoulder injury arose.

The last time Marquez saw action was back in May of 2014, when he won a twelve round unanimous decision over Mike Alvarado at The Forum in Los Angeles.

The knee was giving him problems even prior to the fight with Alvarado. Several planned returns and fights were postponed due to the shoulder issue.

"I don't want to take a risk. These injuries are giving me warnings. First the knee, then after training for two months, training well, running, sparring, and here comes the shoulder injury," Marquez told ESPN Deportes.

"I did some boxing last Tuesday and practically did five rounds of sparring with a good guy with a great future. Afterwards, Nacho Beristáin puts me to do work and in a combination he tells me to do a double hook left and on the second hook, the friction was very strong in the shoulder. It seems that the nerve or something jumped. I have an appointment Monday to do an ultrasound and see practically what issue the shoulder has."

"Hopefully (the injury) is not that serious, so I do not have to go to rehab again. That would break with what I have been training for. We want to see that it is not serious and when we get the results then we will see what is coming. If it is not serious, we will continue the training and hopefully it will not be another injury, because if it is then I would have to decide on the option of retirement."