Frisco, Texas —— Entering play on Wednesday night, Seattle Mariners right-handed pitching prospect Thyago Vieira is 2-1 with a 3.71 ERA over 21 games (26.2 innings pitched) for the Double-A Arkansas Travelers with 23 strikeouts against just 10 walks allowed. I observed the Seattle Mariners’ 23-year-old pitching prospect in the first week of June during a road series in Frisco; below is Baseball Census‘ full Thyago Vieira scouting report, including a video of his outing on June 3 in Frisco.
Thyago Vieira Scouting Report — Video
Here’s Thyago Vieira in a scoreless 1.1 inning outing for the Travelers against the Frisco RoughRiders on June 3:
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Thyago Vieira Scouting Report — Notes
Blessed with plus-plus arm strength, Thyago Vieira works 96-99 mph with his four-seam fastball. He also flashes a two-seam version that’ll sit 94-95 mph and top out at 96 mph, but it doesn’t always have great downward life and can stay on the same vertical plane only to run arm-side. That two-seamer can work very well against righties to get in on their hands, but it can stay out over the fat part of the plate for lefties. The four-seamer is Vieira’s pride and joy, though; his command with it is hit-or-miss, but his control is good enough to play considering the velocity. He likes to throw it, and will go to it in any situation against any hitter.
In addition to the two fastballs, Vieira has a deeper arsenal than most late-inning relievers: a breaking ball, that sits 84-87 mph, and a splitter that sits 90-92 mph. The splitter is raw right now, with poor command and very inconsistent results, but Vieira throws the hell out of it as he’s trying to find a consistent release point. When he catches enough plate with the splitter, he can get some bad swings. He holds the splitter in his hand before coming set in his glove, and will check down to fastball or breaking ball with his grip as necessary. The breaking ball—which Vieira signals as a curve but is more appropriately a true, hard slider—is his best off-speed. The righty throws it extremely hard, like the splitter, but he has a tendency to slow his arm action and body speed to the plate with it at times, tipping the pitch. It’s tough to read out of his hand when right, though, and it spins tight, so when his arm speed is good it’s a wipeout pitch with some downward plane and good late 10-to-4 break.
Command and control have always been an issue with Vieira, even back to his days with the Seattle Mariners’ High-A affiliate in 2016, the Bakersfield Blaze, and it in part stems from inconsistent mechanics. For one, he lands hard on fastballs but significantly softer on off-speed pitches, and it has a tendency to taint his release points a bit. His arm strength is undeniable, though, and that alone will keep getting him looks in the Seattle Mariners’ organization.
Thyago Vieira Scouting Report — Projection
Thyago Vieira is on the Seattle Mariners’ 40-man roster for good reason; he throws the hell out of the ball. That’ll get him a shot in Seattle soon enough, and he’s still just 23 years old with time on his side. But to be a true high-leverage late-inning relief arm in the big leagues he’ll need to improve consistency of his command. Fastballs that get by bats here in Double-A won’t do so as consistently in the big leagues, and beyond that, command inconsistency in both his breaking pitches will hurt him against more refined hitters with better approaches.
All that said, Thyago Vieira is as exciting as they come out of the bullpen in the Texas League, if only just to watch him light up the radar gun with fastballs. Relatively few men have his arm strength—Vieira touched 102 mph last year in Bakersfield on multiple occasions—and that’s enough for a good, long look down the road. Another year of development will get him a shot at late-inning outs in Seattle, and command improvements will ultimately dictate whether he might eventually set up or close in the big leagues.