Rays manager Joe Maddon expects the left-hander to throw a couple more "side pieces" in advance of a simulated game. Howell has thrown breaking pitches, and throwing back-to-back side sessions is next on his ladder of progression.
Maddon would not commit to a date when Howell will return. The pitcher has said he would be back at the end of May.
"It's going to be close," Maddon said. "He's on task right now. He's doing well. Barring any setbacks, it's pretty much the end of the month, beginning of next month right now."