Simmons was drafted by the Atlanta Braves in the second round of the 2010 Major League Baseball draft out of Western Oklahoma State College. Prior to the 2012 season, Simmons was the Braves' fourth-best prospect according to Baseball America. He was ranked 92nd in all of baseball. During spring training he competed with Tyler Pastornicky for the Braves starting shortstop job. On May 30, 2012, the Braves called Simmons up, and he made his Major League debut on June 2 against the Washington Nationals. He got his first Major League hit, a double, on June 3. Simmons was named National League Rookie of the Month for June 2012 after hitting.333 with six doubles, three home runs, and 14 RBIs in June. He led all NL rookies in batting average and on-base percentage. He also won praise for his outstanding defense. On July 8, 2012, during a game against the Philadelphia Phillies, Simmons suffered a non-displaced fracture of the fifth metacarpal on his right hand while sliding head-first into second base. On July 9, he was placed on the 15-day disabled list. In the 2012 National League Wild Card Game against the St. Louis Cardinals, Simmons hit an eighth-inning fly ball to left field that dropped in between Cardinals shortstop Pete Kozma and left fielder Matt Holliday. Simmons was believed by many to have been entitled to a single, but left field umpireSam Holbrook cited the infield fly rule and called Simmons out. Angered Braves fans littered the field with trash, causing a 19-minute delay and a threatened forfeit. The Braves lost the game 6–3 and were eliminated. Simmons had his first full season in 2013, playing in 157 games. He finished the 2013 season with the highest Defensive Runs Saved ever recorded in a year and received the Gold Glove, the Fielding Bible, and the Rawlings Platinum Glove Award for his defensive work that season. On February 20, 2014, the Atlanta Braves signed Simmons to a seven-year deal worth $58 million. In 2014 he batted.244/.286/.331. At the end of the year, Simmons won the Gold Glove and Fielding Bible for his position. In 2015 he batted.265/.321/.338. He had the lowest number of pitches per plate appearance in the major leagues.
Los Angeles Angels
On November 12, 2015, Simmons, along with catcher José Briceño, was traded to the Los Angeles Angels of Anaheim for Erick Aybar, Sean Newcomb and Chris Ellis. In a May 9, 2016, game against the Tampa Bay Rays, Simmons tore the ulnar collateral ligament of his left thumb and was placed on the disabled list. He was reactivated on June 16. For the season, he batted.281/.324/.366, and struck out in only 7.9% of his at bats. He received the Fielding Bible Award for the fourth straight year. In 2017, Simmons hit.278/.331/.421 with 14 home runs and 69 RBIs, and had the lowest strikeout percentage of all major league baseball players. Simmons finished 8th in the American League Most Valuable Player voting. He received his third Gold Glove Award as well in 2017. His Defensive Wins Above Replacement in 2017 was 5.0, third-highest of all time and highest since 1917. In 2018, he batted.292/.337/.417 with 11 home runs and a career-high 75 RBIs, a major-league-leading 28 infield hits, had the lowest strikeout percentage of all major league baseball players for the second consecutive year, had the lowest number of pitches per plate appearance in the major leagues, and led the majors in pull percentage. He also won a Gold Glove for the second consecutive season. As of 2018, he led the major leagues in career at bats per strikeout. He was placed on the disabled list on May 21, 2019 with an ankle injury.
