Back trouble

That really sucks. From the score, I can even guess that his injury happened somewhere in the second set...

As usual. Physically too weak. Shoganai.

like ive said before the smaller guys have to push themselves that little harder. im guessing he will have similar problems like Hewitt. injuries held back Hewitt in the second half of his career. Kei has very similar physique and playing style of Hewitt.

Get better, and go get 'em, Kei-san ! Hope to see you at Roland Garros ! Ganbarre, Kei-san !

I wonder if the way he leaps up in the air everytime he makes a shot is causing his lower back problem.

welcome to the reality of tennis, one of the most grueling of sports. I would say it requires some of the most stamina, yet requires so much mental. Kei does alot of training on his back, but is just a sport that puts alot of stress on the lower back because of spin serves, stretching at weird angles for balls, etc. And am sure the air kei shot puts him at more risk for injury. He may have to resort to cortisone shots and alot of ibuprofen.

Lower back pain and injury is common among tennis players. It may have various causes such as postural abnormalities, muscle imbalances, overuse, instability, and articular dysfunction in the lower back. In tennis, the combined rotation, flexion, and extension of the back during the serve may cause problem. Rest, medications and ice are usually recommended to relieve pain and muscle spasm but in the event of serious cases, he would have to consult a sport physician or a sport physiotherapist for treatment.