Yu Darvish dealt with nerve problem

ARLINGTON, Texas -- Texas Rangers ace Yu Darvish suffered from a nerve problem in his lower back and buttocks area from the beginning of September through the end of the team's season, a source familiar with the situation told ESPNDallas.com on Wednesday.

The issues caused numbness in Darvish's right leg, the source said. Darvish could be seen several times toward the end of the season tapping the area with his right hand between pitches.

Darvish alluded to a physical issue after a start at Tampa Bay in the second-to-last week of the season, but he didn't reveal the nature of the injury.

Darvish did not make it out of the sixth inning in any of his final three starts, beginning with the one Sept. 19 against the Rays. He was 1-3 with a 3.34 ERA in September.

The source said that the symptoms flared up at different times during each of Darvish's outings.

That could explain why Darvish's fastball velocity was down at the end of the season. The right-hander averaged 91.3 mph on fastballs at Tampa Bay, according to FanGraphs.com. He averaged 91.7 mph in starts at home against Houston and Tampa Bay in the final week of the season.

On the season, however, Darvish averaged 92.9 mph on fastballs.

Rangers manager Ron Washington said Tuesday that Darvish was dealing with a physical issue but wouldn't elaborate.

"I don't think I can even get into that," Washington said. "I'll let you all talk to people above me and the medical staff. But I can say this -- he never said it was an issue."

Darvish spent time on the disabled list in 2009 with lower back pain while pitching for the Hokkaido Nippon Ham Fighters of the Japan Pacific League. He also had similar problems during the 2008 season.

The Dallas Morning News earlier reported the nature of Darvish's injury.