The always trade-aggressive Seattle Mariners made a move on Friday morning to address their rotation depth, but it came at a high cost. Seattle traded outfield prospect Tyler O'Neill to the St. Louis Cardinals in exchange for starting pitcher Marco Gonzales.
Gonzales comes over from the Cardinals after he spent much of the season in Triple-A Memphis. Across 11 starts for the Redbirds, Gonzales posted a 2.90 ERA, 0.79 HR/9 and 57/17 K/BB ratio. While the ERA is low and Gonzales kept the walks and home runs down, his 4.18 fielding independent pitching (FIP) and 9.4 percent swinging-strike rate indicated more issues than the ERA showed.
The 25-year-old southpaw, a first-round selection in the 2013 MLB Amateur Draft, received another brief glimpse of the majors for the second time in his career when St. Louis called him up for a spot start on June 13. In 3 1/3 innings against the Milwaukee Brewers, Gonzales surrendered six hits and three home runs to 16 batters faced and departed with five runs allowed.
It's been a long road for Gonzales, whose once promising profile became derailed by shoulder injuries in 2015 and Tommy John Surgery to begin 2016, but his return to the mound with these numbers demonstrated he is healthy and could still be an effective pitcher.
While he doesn't carry significant upside, Gonzales is nearly major-league ready and could turn into a very stable option that can eat innings and turn out some quality starts in the back-end of a team's rotation with the future to be a middle-rotation arm.
He should be up in Seattle fairly soon and help try and improve its rotational depth and consistency.
For the Cardinals, this move is an easy one to make. They buy low on O'Neill, who entered the season rated as the 29th-best prospect in all of baseball by MLB Pipeline.
Billed with 70-grade raw power and the potential to one day hit 30-plus home runs as a corner outfielder, O'Neill vaulted himself into the upper echelon of prospects after an outstanding year in Double-A last season.
Across 575 plate appearances for Double-A Jackson, O'Neill posted a .293/.374/.508, .398 wOBA, 152 wRC+, 19 home runs and .882 OPS. The home run totals were a slight dip from the 32 he hit in 2015, but his slash line and overall numbers showed great improvement.
The jump up to Triple-A Tacoma proved to be a difficult challenge for the 22-year-old. In 396 plate appearances, his slash line dropped to .244/.328/.479, with a .347 wOBA, 104 wRC+ and an .807 OPS. But he still hit 19 home runs over that time and his isolated power is 20 points higher than in 2016.
To make matters even better, O'Neill has turned things around since a miserable first two months of the season. From April 7-May 30, O'Neill posted a .216/.288/.383 slash line with a .672 OPS, .168 ISO and five home runs in 212 plate appearances.
Once the calendar turned past May, everything turned around. Across his last 184 plate appearances, O'Neill hit 14 home runs, carried a .314 ISO, .966 OPS and a .277/.375/.591 slash line.
So while young, southpaws with contract control are very valuable and it filled a need for Seattle, St. Louis could be walking away with a young hitter that could blossom into a middle-of-the-order bat whose power fits perfectly into today's game as a corner outfielder.