Sánchez signed with the Chicago White Sox as an international free agent in 2009. He played in the Dominican Summer League for the DSL White Sox in 2009 and 2010. The next season, playing second base primarily, he split the year between the Bristol White Sox of the Rookie-levelAppalachian League and the Kannapolis Intimidators of the Class ASouth Atlantic League, finishing the year batting.286/.354/.343 batting average with 30 runs batted in and 48 runs scored in 68 games. During the 2012 season Sánchez moved quickly through the White Sox system. He started the season with Class A-Advanced Winston-Salem then moved to Double-ABirmingham Barons, and then eventually Triple-ACharlotte Knights. He was named to appear in the 2012 All-Star Futures Game while playing for the Winston-Salem Dash of the Class A-Advanced Carolina League, and was named a Carolina League Post-Season All Star. Sánchez hit a combined.323/.378/.403, 169 hits, 1 home run, 25 doubles, 7 triples, 79 runs, 56 RBI, 26 stolen bases in 133 games. He was named an MILB.com Organization All Star. The White Sox invited Sánchez to spring training as a non-roster invitee in 2013, and he ranked as the White Sox #4 prospect. Sánchez spent the entire 2013 season at Triple-A Charlotte, where he batted.241/.293/.296 in 432 at bats, 50 runs, 20 doubles, 2 triples, no home runs, 28 runs batted in, 29 walks, 76 strikeouts and 16 SBs. Sánchez was added to the 40-man roster on November 20, 2013. On July 13, 2014, the White Sox promoted Sánchez to the MLB roster and he made his MLB debut that same day going 0-5 with two strikeouts. Sanchez was sent down to Charlotte after the game, but was recalled to Chicago on August 22, after the White Sox traded Gordon Beckham. In 2014 with the White Sox he batted.250/.269/.300 in 100 at bats. He was named an MILB.com Organization All Star. In 2015 with the White Sox he batted.224/.268/.326 in 389 at bats, and in 2016 he batted.208/.236/.357 in 154 at bats. Sánchez announced that he would go by his first name, Yolmer, starting from the 2017 season, rather than his middle name of Carlos. In doing so, he became the first player named Yolmer in Major League Baseball. In 2017, he batted.267/.319/.413 with a career-high 12 home runs in 484 at bats, and was 2nd in the AL with 8 triples. In 2018, playing third base primarily, he batted.242/.306/.372 in 600 at bats with a career-high 14 stolen bases, and led the AL with 10 triples. He received the MLBPAA White Sox Heart and Hustle Award. In 2019, playing second base primarily, Sánchez batted.252/.318/.321 in 496 at bats with two home runs and 42 RBIs, with the lowest slugging percentage and Isolated Power in the major leagues, and the highest opposite field percentage of all major league batters. On defense, he turned 108 double plays and had an 11 Defensive Runs Saved rating, both the best in the American League among second basemen. He won a Gold Glove Award at second base. Sánchez was released on November 25, 2019.
