- Full name Thyago Vieira
- Born 07/01/1993 in Sao Paulo, Brazil
- Profile Ht.: 6'3" / Wt.: 265 / Bats: R / Throws: R
- Debut 08/14/2017
Organization Prospect Rankings
When the Mariners signed Vieira in 2010 as a 17-year-old for just $65,000, they saw a raw arm with the potential to light up radar guns as he matured. They were, in a word, right. Vieira became a must-see minor league who lit up radar guns as high as 104 mph and made his major league debut in August. The Mariners dealt him to the White Sox after the season in exchange for international slot money to help the Seattle's unsuccessful pursuit of Japanese two-way star Shohei Ohtani. Vierira, along with Michael Kopech and Zack Burdi, is part of a trio of White Sox prospects who have touched at least 102 mph with their fastballs. He couples the pitch, which typically sits in the 98-100 mph range, with a fringe-average slider and a developing changeup in the low-90s. He's also working on a split-fingered fastball. If that takes, he could quickly become a back-end of the bullpen stalwart. Vieira, who has an effortful delivery, still needs to improve his command to up his odds of finding a spot as a high-leverage bullpen arm. He's likely to head to Triple-A Charlotte to begin the 2018 season.
Vieira signed with the Mariners for $65,000 as a raw 17-year-old international free agent in 2010. Early in his career he showed arm strength and not much else, and he was best known for closing for Brazil's 2012-2013 World Baseball Classic teams. He finally made a developmental leap in 2016 under high Class A Bakersfield pitching coach Ethan Katz. Katz streamlined Vieira's delivery to allow his arm to power through free of moving parts, and the result was a consistent 96-100 mph fastball that hit 102 at the end of the season. His command also improved dramatically to average, and his 89-92 mph slider sharpened to become an above-average pitch. The result was the highest strikeout rate (10.8 per nine innings), lowest walk rate (3.7), fewest hit batters (two) and lowest ERA (2.84) of Vieira's career in 2016. He had one midsummer stretch where he didn't allow an earned run for six weeks as Bakersfield's closer, and overall he allowed only one home run all season. The Mariners rewarded him with an assignment to the Arizona Fall League, where he touched 104 mph with his fastball and began flashing a promising curveball as well. Vieira has to prove he can maintain his delivery and command, but his raw stuff is that of a dominant late-inning reliever or closer. He will start 2017 at Double-A Arkansas.