Oscar Mercado was showing a lot of improvements offensively since being switched to the outfield. He was also a speed threat and very good defensively. The St. Louis Cardinals would have been able to utilize his skill set in some way in the future. Instead, he was traded for a pair of outfielders.
According to MLB Pipeline, this trade was essentially a wash. Mercado was number 10 on the Cardinals list, and Conner Capel was number 14 for the Indians. They took each others spot in their new organizations.