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St. Louis Cardinals snag Tyler O’Neill from Seattle Mariners for Marco Gonzales

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The Seattle Mariners continue to use prospects to barter, this time landing themselves a young starter for a Wild Card push.

MLB: Game 2-Milwaukee Brewers at St. Louis Cardinals Jeff Curry-USA TODAY Sports

There has to be some sort of nickname for Jerry Dipoto by now. The Prospect Slinger? The Monty Hall of the prospect world continued his transformation of the Seattle Mariners by bringing in Marco Gonzales for Tyler O’Neill.

Marco Gonzales, LHP

Most people know the skinny on Gonzales by now. The now-25 year old left-hander was drafted by the St. Louis Cardinals in the first round back in 2013 out of Gonzaga. By 2014 he was one of (if not the) top-ranked Cardinals prospect, and by the end of that season he was in the big leagues.

Gonzales went 4-2 over 10 appearances (five starts) with a 4.15 ERA and a 1.53 WHIP, striking out 31 and walking 21 in 34.2 innings. The Cardinals hoped he would take the next step in 2015, but that’s when things kind of went off the tracks.

His 2015 was shortened by shoulder soreness. John Sickels reported in his The Prospect Book 2016 that Gonzales’ already-low velocity on his fastball had dropped. His curveball also had lost its consistency and bite, and he struggled mightily, despite his change still being a weapon. He then lost his entire 2016 to Tommy John surgery.

Gonzales looked back to form in the Pacific Coast League this season. He was 6-4 with a 2.78 ERA and a 1.04 WHIP. Gonzales struck out 64 in 74.1 innings with a much improved 2.24 walks-per-nine rate. Baseball America reports that his velocity is back up to the low-90s as well. He know heads to Seattle, somehow still with his rookie status in tact. The Mariners get a young, 25-year-old southpaw on the rebound under cost control through at least 2020.


O’Neill has always been one of the Mariners more exciting prospects, ever since he was their third-rounder in the 2013 MLB Draft. His quick right-handed swing broke out in the California League in 2015. That year, he slashed .260/.316/.558 with a career-best 32 home runs and 21 doubles, while swiping 16 of 21 stolen base attempts.

Of course, O’Neill wouldn’t have been the first to breakout in the home run-happy Cal League. All eyes were on the now-22-year-old right-fielder as he headed to the more pitcher-friendly Southern League with the Jackson Generals.

O’Neill didn’t disappoint.

He was an All Star both in the Southern League and on Baseball America’s year-end list. O’Neill earned his first Future’s Game nod. Come the fall, he was named to the Arizona Fall League Rising Stars list. And in between, he was both the Southern League regular season and Championship Series MVP en route to the Generals 2016 CL Championship.

O’Neill slashed .293/.374/.508 with 24 home runs, 26 doubles and 12 stolen bases. He remained very strikeout heavy (150 in 575 plate appearances) but finally countered that high-rate with a career-best walk rate of 10.8 percent.

John Sickels named O’Neill the second best Mariners prospect heading into 2017. Here’s what he had to say:

Age 21, third round pick in 2013 from high school in Canada; hit .293/.374/.508 with 24 homers, 62 walks, 12 steals, 150 whiffs in 492 at-bats in Double-A; 65 power, maybe even a 70, due to outstanding bat speed and strength; has improved reads on breaking balls but still strikes out a lot, threatening to impede batting average and OBP at higher levels; that said, if he can hit .250-.260 the power will be enough to play regularly and he’s shown ability to make adjustments; high school catcher has developed into an under-rated right fielder with a strong arm and more range than you’d expect; ETA late 2017.

He got off to a slow start this year in the PCL and the naysayers quickly began their critiques. O’Neill quickly silenced them with an enormous July, slashing .317/.394/.730 blasting eight home runs. While he remains a free-swinger, his season walk rate has again improved to a career-high. Continual improvement there is always promising.

You would never guess the 5-foot-11 slugger is one of the more exciting power-hitters in the minors, but it’s time to accept that he just may be for real. That bat is pretty darn quick and he clearly has the strength to muscle the ball to all fields. He certainly has swing-and-miss issues, but has shown that he continually learns patience and quits chasing.


O’Neill seems like a Cardinals type of guy. He’s transformed himself successfully from catcher to a pretty solid right-fielder. They will likely find a way to get the most out of him. It will take a trade to get him to the big leagues soon, but expect him to make a push for the 2018 Opening Day roster.