"Jefferson is a plus defensive catcher with an excellent frame for the position," said Marco Paddy, White Sox special assistant to the general manager, international operations. "His abilities to handle a pitching staff and call a game should help him develop quickly."
No terms of the signing bonus for Mendoza were revealed, but the White Sox can't sign any international amateur player for more than $300,000 over the next two signing periods. They went over their current bonus pool by agreeing to a Minor League deal with Cuban outfielder Luis Robert, including a $26 million signing bonus.
Robert, 19 and the No. 23 overall prospect per MLBPipeline.com, signed on May 27 and has a .277 average over 47 at-bats with the White Sox Dominican Summer League team. But of greater importance is his .500 on-base percentage, with 16 walks against 12 strikeouts.
"I saw video of his [lone] homer," said White Sox hitting coach Todd Steverson of Robert, who has four RBIs and seven stolen bases to go with his one homer. "It's hard to hit a homer down in the Dominican. People don't realize how thick that air is with the humidity down there. For him to be able to do that, it's pretty good.
"He's very athletic, real loose. I mean by loose he's got some quick hands. He's got a fluid body."
Mendoza joins outfielders Josue Guerrero (2016), Franklin Reyes ('15) and Micker Adolfo ('13) and infielder Amado Nunez ('14) among the White Sox most recent international signings. Adolfo is ranked by MLBPipeline as the No. 21 prospect in the White Sox organization.