Diaz, 24, possesses all the attributes -- pitch calling, blocking and framing; synergy with pitchers and, above all, a powerful arm -- which in 2015 he demonstrated in his first full season at the Triple-A level.
For several years, Diaz had received "best tools" raves in whichever league he played. The ratings became more meaningful in the International League and confirmed he is on the doorstep to the Majors after he deterred opponents' running game for Indianapolis.
Actually, he already got his foot in that door in September, called up by the Bucs when the roster expanded. Diaz got a couple of pinch-hit at-bats, but other than occasionally warming up pitchers between innings, he has yet to catch a big league pitch.
Nonetheless, the experience on the big league bench furthered his development.
"I've learned a lot," Diaz said upon being added to the Pirates' 25-man roster for the National League Wild Card Game, presented by Budweiser, for an emergency. "So much more of the game is mental in the big leagues, especially with all the scouting reports and information you have on all the hitters. I've learned a lot just being in the scouting meetings and listening to coaches and other catchers talk."
The 6-foot, 210-pound Venezuelan's bat the last couple of seasons has caught up to his established defensive reputation. Diaz batted .236 in his first five seasons in the Pirates' system, through a 2013 season that still found him in A-ball.
In 2014-15, however, while climbing the ladder all the way to Triple-A, he hit .292, with 101 RBIs in 684 at-bats.
Curious to see for themselves, the Pirates brought Diaz to Spring Training for the first time this year and watched him validate all the scouting reports.
"We like what we've seen," said manager Clint Hurdle. "He's done nothing but continue to do well. He continues to give us a lot of reasons to think he's going to be able to impact our club in the future. And the bat showed up."
Diaz went 7-for-16 (.438), with a homer and a double, in exhibition play before being reassigned to the Minor League camp.
"Obviously, the throw lights you up," General manager Neal Huntington said. "He's a guy we're looking forward to help grow and develop and see where he takes it."
Hurdle "absolutely" sees Diaz as a future big league starter.
Will that future arrive in 2016 in Pittsburgh? Unlikely, since both parts of 2015's terrific catching tandem -- Francisco Cervelli and Chris Stewart -- remain under club control and, while both are eligible for arbitration, their 2015 salaries added up to a bargain $2,212,500.