NEW YORK -- Brian Cashman said that the Yankees have deployed every available tool to examine Masahiro Tanaka's health and mechanics, and the general manager sounds convinced that the right-hander will be able to bounce back from his current slump.
"We've done the 'CSI: The Bronx' on him a number of different times," Cashman said on Thursday. "We've gone through the analytics comparison from when he's flying high to the current low. There are no indicators other than the splitter's not splitting like it usually does, and the command of the fastball is off."
Cashman said that the Yankees called upon both advanced statistics and biomechanics to examine Tanaka's velocity, swings and misses in the strike zone, extension and release point. There were no red flags raised, he said, adding to the mystery.
Tanaka has permitted 14 earned runs in his past 4 2/3 innings (27.00 ERA) after going 5-0 with a 2.78 ERA in his previous five outings, and he will start Friday's series opener against the Athletics.
"Other teams are doing damage against him, but there's no indicator of an injury," Cashman said. "I know the player doesn't feel that he's hurt, and I know the pitching coach [Larry Rothschild] doesn't feel there's an injury relation, either."
Tanaka sustained a partially torn ulnar collateral ligament during his first season with the Yankees in 2014, and Cashman said that nothing in the hurler's history has urged the Yankees to send him for a checkup MRI this year.
"From an analytics standpoint and front-office perspective, we can't seem to come up with some reason that would lead us to take that step," Cashman said. "We're not afraid to do it if we felt that was necessary, but we're not going to do something that appears to be unnecessary."
No timetable for Ellsbury
Cashman said that the Yankees do not know how long they will be without outfielder Jacoby Ellsbury, who sustained a concussion in Wednesday's 3-0 victory over the Royals. Ellsbury has been placed on the seven-day concussion disabled list.

"Those concussions hopefully can clear up quick, but I'm not going to presume that it will, either, because they're all based on the patient and how they're responding over time," Cashman said.
The Yankees recalled infielder-outfielder Rob Refsnyder from Triple-A Scranton/Wilkes-Barre on Thursday, and they plan to have Aaron Hicks play regularly in center field alongside Brett Gardner and Aaron Judge. Cashman said that he was not inclined to add prospects Dustin Fowler or Clint Frazier to the 40-man roster at this time.
"I have no one to promote from Triple-A that would start ahead of any of these guys that we have," Cashman said.