Mercado was added to the 40-man roster Monday. Prior to the 2017 season, Mercado's bat had been on the quiet side. His batting average had never climbed above the .254 mark, and his OPS peaked at .638. However, he had a great showing at Double-A Springfield. Over 120 games he slashed .287/.341/.428 and hit 13 home runs. Additionally, he showed the ability to be a threat on base as he swiped 38 bags in that time. By adding Mercado to the 40-man roster, the Cardinals will protect him from the Rule 5 draft.
Mercado, 22, is hitting .289/.340/.436 with 12 home runs, 40 RBI and 35 steals in 105 games at Double-A Springfield. Mercado was previously a shortstop who hit .215 with zero home runs in 2016. Flash forward one year, Mercado is manning the outfield while showing surprising pop, and his speed remains above-average. The suddenly toolsy Mercado appears to have revitalized his career with the move to the outfield.
Mercado, a former shortstop who is now manning center field for Double-A Springfield, is slashing .325/.395/.506 over 87 plate appearances across 19 games. The 22-year-old is also sporting a .901 OPS and is just one home run short of the career-high four he posted over 513 plate appearances at Low-A Peoria in 2015. All the components of Mercado's slash line represent personal bests, and he's added six stolen bases on 10 attempts to his overall production. While he's generated plenty of encouraging numbers, the one area of concern for the promising prospect is a strikeout rate that's shot up to 26.4 percent and a contact rate that's down 14 percent from last season. His .431 BABIP should naturally also come down over time, but for the moment, Mercado is displaying more pop relative to playing time than at any other point during his four-plus professional seasons.