Johnson said Vanderbilt was lucky to hang onto Gray. What spawned was an impactful relationship that stretched beyond just baseball.
"He's a pretty special person to me," Gray said. "He was one of those father-figure types you hear people talk about -- especially at an important part of my life."
Gray doubled as a hard-throwing pitcher and a two-time state champion quarterback at Smyrna High School in Tennessee. Johnson said Gray's athleticism -- something that he believes is a key to Gray's success in the big leagues -- was evident immediately.
"He was kind of a no-brainer type of guy, it was just a matter of whether we were going to keep him or not," Johnson said.
Gray stayed at Vanderbilt for three years. He was brought along slowly, spending the first half of his freshman year as a reliever, but ultimately ascended to rotational anchor, going 12-4 with a 2.43 ERA and 132 strikeouts in his junior season. He did so under the tutelage of Johnson, who coached other big leaguers such as David Price, Mike Minor and Jason Frasor.
Gray said Johnson would often quiz him on specific baseball situations geared toward life as a professional, even asking him how he'd handle himself on the mound at places like Yankee Stadium. Gray, in turn, would need to react purposefully.
"He's one of those guys that looks at the individual pitcher and assesses from there," said Gray, adding they often focused on the mental side of pitching. "He's not someone where it's a certain way to do anything. He's very open-minded."
Johnson, who coached 11 seasons at Vanderbilt (2002-12) and was the Cubs' Minor League pitching coordinator from 2013-15, saw a fiery pitcher capable of anything on the mound.
"He's very competitive," Johnson said. "He knows how to make adjustments mid-stream. I think that's the quarterback in him as much as anything. He has the ability to improvise in a situation."
Gray's blossomed into an All-Star and one of baseball's brightest young pitchers, but 2016 has been a trying season for the righty, who is 3-6 with a 5.20 ERA and posted a 9.61 ERA in May before going on the disabled list.
"He really hasn't struggled much to this point in his entire career," Johnson said. "I think guys go through those peaks and valleys, and it was a valley for him."
Gray's 0-1 with a 3.28 ERA in his last four starts and was sharp Tuesday, striking out seven Brewers in six innings. Johnson said he wasn't surprised Gray would eventually encounter difficulties, but he also wasn't surprised he's working out of them.
The two remain in frequent contact, trading texts every so often, and Gray continues to seek advice from Johnson. He relishes any opportunity to catch up with his "mentor," adding "we definitely care about each other."
That Johnson sat in an opposing dugout in a Major League stadium, a situation they spent years preparing for, made it all the better, even if it was the first time Johnson was wearing the opposition's colors.
"It's hard to imagine when you're doing it, heck, I guess it was six years ago now," Gray said. "But you always wish that's the case. It's pretty cool that ended up happening."