Darvish reportedly has a sciatica: A form of discomfort in the lower back. It is often caused by either compressed nerves or a protruding disc. The injury caused Darvish to feel numbness down his right leg since the beginning of September.
Other symptoms of a sciatica can include pain in the lower back, difficulty controlling or moving the leg, and a pins and needles sensation.
Manager Ron Washington said during an end-of-the-year interview that Darvish never let on that it was an issue. However, it could explain why Darvish failed to pitch a full six innings during any of his last three outings. He was also uncharacteristically wild at times and lost over one mile per hour on his fastball over the final month.
The fact that Darvish had these issues also makes his performance late in the season that much more impressive. Over his last five starts, he posted a 2.40 ERA while striking out 37 batters over 30 innings.
Darvish missed time in 2009 while pitching in Japan with a lower back issue, but it is not known if that was also caused by a sciatica.