"He was like, 'Are you trying to pitch around guys? Are you trying to pitch different? Why aren't you going after guys?'" Santiago told MLB.com on Monday of Cooper's weekend assessment.
"It was a little bit louder than the way I just said it," added Santiago with a laugh.
Pinpoint control has not been Santiago's forte this season, but he has been able to shake loose early struggles outside the strike zone in most starts to turn in a solid effort during his first season as part of the rotation. But Friday's self-described worst start of the year serves as a lesson in the growth process for a young pitcher and even a young catcher in Josh Phegley.
After getting squeezed on fastballs inside during the first inning Friday, by Santiago's estimation, he altered the game plan and stopped going inside. Santiago has the ability to throw six pitches, but throwing first-pitch breaking balls and sliders moved away from what Santiago wanted to do.
His goal is to simplify things when taking the mound for Thursday night's start in Baltimore, focusing in the early going on just fastballs and changeups. That's the blueprint he followed last September in Cleveland when Santiago one-hit the Indians over seven innings
As for Cooper's tough love, Santiago understands it's all geared toward improvement.
"You definitely appreciate him trying to get after you about what you are thinking right there in that situation," Santiago said. "When you are doing good, you want him to help you out just the same way.
"If you are out there and go six innings and have three walks, you still want to hear that tough feedback. He can give you both sides of the good and bad. It was definitely different. Coming in the dugout that day, it was a little blowup session. It was kind of aggressive, and I wasn't expecting it. It caught me off guard. It hasn't happened all year."
Scott Merkin is a reporter for MLB.com. Read his blog, Merk's Works, and follow him on Twitter @scottmerkin. This story was not subject to the approval of Major League Baseball or its clubs.