RHP Matthew Thompson ranked in Mariners’ spot (#20) in latest Baseball America Draft Ranking

One of the top prep pitchers might be available to Seattle

While it’s prospect ranking season (check out our countdown of the top 50 Mariners prospects here), it’s also time to start thinking about the 2019 MLB draft, which is especially early this year, beginning June 3. Baseball America has compiled their list of the Top-200 draft prospects, and while names will filter up and down the list over the next few months as prospect stock rises and falls, it’s useful to check in and see who might be available around where the Mariners pick at #20 overall.

It’s important to note that this list doesn’t exactly correlate with Baseball America’s mock drafts, which are often created by talking with scouts or internal sources in an organization, or simply noting which teams regularly send scouts to certain players’ showcase events. BA’s most recent mock draft, released about a month ago, has the Mariners selecting UNLV SS Bryson Stott—I wrote a brief summary of him here, which ended with me questioning if the defensive wizard would even be available to the Mariners at that position. Things change quickly in the prospect ranking world, though, and Stott has fallen to #27 in BA’s Top-200 ranking.

In the latest Top-200, spot #20—where the Mariners will pick—is currently occupied by Texas high school RHP Matthew Thompson, who was projected to either Tampa Bay (#21) or Atlanta (#22) in BA’s mock draft. This is exciting to me because in watching the latest Perfect Game All-American Classic—a report on which is coming—Thompson was one of my standouts.

Standing 6’2/185, the 18-year-old Thompson looks like the prototypical pitcher, with plenty of projection left on a long, lean, athletic frame. Thompson has a balanced delivery with good extension out of a high ³⁄₄ slot that initially caused him to get tagged with the dreaded “high-effort” label by some scouts, but he’s simplified his mechanics to be much smoother and more fluid and now is the recipient of much praise for his lightning-fast, explosive (but still smooth!) arm action. Just try to catch up with how quickly his arm moves here:

Thompson’s fastball velocity has steadily climbed from the high 80s to the low 90s, even being clocked as high as 96, with some good sink. At the Perfect Game event Thompson was between 93-95 in his inning and showed an ability to place the pitch all over the zone. Some see the fastball as too straight, but note his quick arm action and high arm slot help create a good downhill plane.

Thompson’s real weapon is his nasty, tight, knee-buckling low-to-mid-80s breaking pitch that makes righty batters, especially, look foolish. BA and FG both call the pitch a slider, while Perfect Game calls it a power curve.

Tagging the pitch a slider is probably due to its velocity, and the tendency of the pitch to take a late, sharp dive away from righty batters, inducing some ugly whiffs. Thompson can also struggle with command, leading me to think what’s called a slider is actually a curve that’s gone rogue, but the distinction is fairly academic when it results in this:

Thompson also gets high marks for his makeup, and while he’s a competitor, he also loves baseball and keeping things loose, which seems like a good fit from an organizational standpoint. I’d smile too if I threw that pitch.