Santana pitched his longest outing to date on Thursday, throwing four innings in extended spring. The lefty threw 10 additional pitches after that to get up to 58 overall. His velocity, which has been in the mid-to-upper 80s in previous outings, was also good, although Showalter wouldn't divulge an exact number.
"[He] threw the ball well," Showalter said. "Highest he's been [velocity-wise]."
Rehab assignments for pitchers can last up to 30 days, although there are ways around that if Santana were to have a setback. So far, it's been nothing but positive as the former Cy Young Award winner works his way back from a second shoulder surgery in three years.
Signed to a Minor League deal with incentives this spring, Santana is hoping to be a starting option for the Orioles by June.
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.