Yusei Kikuchi was taken off the active roster on May 6 because of tightness in his left shoulder. The condition is not new (may have originated with neck pain from sleeping wrong back in March 14) and is also not considered serious (no pain, just tightness). He will be examined at a hospital as a precaution.
Kikuchi threw 104 pitches and allowed five runs over six innings during his last start on May 4. The Seibu Lions decided to take Kikuchi off the active roster after confirming the condition of his shoulder the following day on May 5.
[UPDATE 5/10 @ 3:59am]
Kikuchi was examined at a hospital in Tokyo on May 8 and diagnosed with decreased functionality in his shoulder. He will spend some time strengthening his shoulder and ultimately hopes to make it back to Ichi-gun in two to three weeks.