Acquired with Vic Black from the Pirates last year for John Buck and Marlon Byrd, Herrera reached Double-A on June 19, and hit, and hit, and hit.
In 30 games in Double-A, Herrera -- who turned 20 in March and is the youngest position player at the entire level -- has hit .323/.375/.459 with 10 doubles and four home runs. He's hit safely in 12 straight games. He's hitting for more power in Double-A than ever before, and walking more, too. Let's go to the advanced stats to learn something about the shape of Herrera's recent production:
These numbers are from partial seasons, and Herrera has only had 138 plate appearances in Double-A. Strikeout and walk rates begin to stabilize around 100 plate appearances, homers at 150, while hits can take two full seasons to normalize, even in the big leagues. Let's get this out of the way first: his .435 batting average on balls in play is not going to last. When that comes down, it will pull his whole line down.
On the other hand, he's walking in 10 percent of his Double-A plate appearances, which brings his yearly total to 7.2 percent. That's still below big league average (8.5 percent) but is not far off. And the power? Well, his isolated slugging percentage in Double-A (.213) is far higher than what he posted in St. Lucie or in the South Atlantic League in 2013. However, taken together, his extra-base hit rate of 8.3 percent in 2014 almost identical to his 2013 rate (8.2 percent).
Herrera worked to eliminate his leg kick and simplify his swing in St. Lucie, and the result has been a lower strikeout rate this year. He's struck out fewer times in Double-A, against the best pitching he's seen in his life, than he did in Single-A.
So, what's real, given sample size? The drop in his strikeout rate is. The improvement in his walk rate might be. And his power is similar to last year. He's improved his skills against tougher competition this year, a nice marker for a prospect.
And when will Mets fans see Herrera? That's a good question. The team just recalled Wilmer Flores to help out in the middle infield. Daniel Murphy might or might not be traded now or in December. In any case, the team needs to add Herrera to the 40-man roster this winter to protect him from the rule 5 draft.
Given that, if he's still raking in September, the team could make a 40-man move early to give Herrera a big league look in the season's final month, when rosters expand. Otherwise, Queens should see him sometime in 2015.