- Bats Right, Throws Right
- Height 6' 2", Weight 175 lb.
- High School Gaither High School
Lanky Oscar Mercado was a second-round choice by the St. Louis Cardinals in the 2013 amateur draft. He began his career that season with the GCL Cardinals where he hit .209 in 42 games as the team's primary shortstop. In 2014, he hit .224 in 60 games for the Johnson City Cardinals but scored 41 runs and drove in 25 in spite of a low BA and OBP (.303). He showed some unexpected power with 9 doubles and 3 homers and also stole 26 bases in 33 attempts, after going 12 for 16 his first year. In 2015, he moved up to the Peoria Chiefs of the full-season Midwest League, where he hit .254/.297/.341 in 117 games; he also committed 41 errors at shortstop. He scored 70 runs and stole 50 bases, but was also caught 19 times.
In 2016, he moved to the Palm Beach Cardinals of the Florida State League and began splitting his time between shortstop and the outfield. He continued to struggle in the batting average department, hitting 215 with an OBP of .296. He scored just 50 runs and while he stole 33 bases, he was caught 20 times. In spite of his inability to so far turn his potential into actual production, he was a late addition to the Colombian national team for the 2017 World Baseball Classic, taking advantage of some Colombian ancestry. The team was looking for outfielders, with Tito Polo and Efrain Contreras as the only true fly-chasers on the team, but they especially wanted Oscar for his foot speed. Indeed, he was used twice as a pinch-runner in the tournament, both times coming in for DH Jhonatan Solano. Against Canada, he played his role perfectly, scoring an important insurance run in the 9th inning. Then against the Dominican Republic, he replaced Solano at first base with nobody out and the score tied 3-3 in the 9th. He moved to third base and when Reynaldo Rodriguez hit a line drive to shallow left with one out, he took off at full speed to challenge Jose Bautista's arm. He was nailed by a perfect throw by the slugger not normally known by the strength of his arm as C Welington Castillo tagged him on the leg just before he touched the plate, sliding head first. It was an extremely close play and both Rodriguez and Polo were ejected for arguing umpire Tripp Gibson's call a little too forcefully. Even though he was nominally the DH, he had to be inserted into the defensive line-up after the ejections, playing RF. The Colombians eventually lost the game, 10-3, after the D.R. exploded for 7 runs the 11th inning and Mercado made an out in his only at-bat to end the game. Colombia was eliminated, but had he beaten Bautista's throw, they would have won the game - and also finished first in the Pool thanks to the tie-breaking formula.