Although his fastball is not an out pitch for him, Yamaguchi’s success with his splitter this season and to a lesser extent his slider is probably related to an uptick in four-seam fastball velocity. 
Rotation depth is the top priority for the Toronto Blue Jays this offseason and, last week at the Winter Meetings, they added veteran innings-eater Tanner Roark on a sensible two-year contract. The Blue Jays are now set to add another free-agent starter.
Yamaguchi, 32, has been among the top starters in Japan the last few seasons. He threw 181 innings with 194 strikeouts and a 2.78 ERA this past season, and he has experience as a starter and as a reliever. Here’s a mini-scouting report from veteran Japanese baseball reporter Jim Allen:

The Blue Jays have an excellent young position player core in Bo Bichette, Cavan Biggio, Vladimir Guerrero Jr., and Lourdes Gurriel Jr. Inexperienced, yes, but awfully talented. The rotation was a major question mark coming into the offseason, and although the Blue Jays didn’t bring in a no-doubt ace, they’ve added depth in Anderson, Roark, and now Yamaguchi.
That is decent enough depth, but clearly, the Blue Jays still have room for another established big-league starter. The club has been connected to free agent southpaw Hyun-Jin Ryu in recent days. I can’t imagine Yamaguchi’s relatively small contract will stand in the way of a potential Ryu deal, if Toronto is truly willing to spend what it takes to get him.
MLB scouts I’ve spoken to see him as either a back-of-the-rotation starter or a bullpen guy,” Allen added. Yamaguchi will be the fifth Japanese-born player to suit up for the Blue Jays and the first to join the team directly from Japan. Tomo Ohka, Ryota Igarashi, Munenori Kawasaki, and Nori Aoki all spent time with other MLB clubs before joining Toronto.

With the Giants, Yamaguchi’s splitter has come into its own, and this season he not only executed it well but also incorporated it into his entire mix better so that batters were going after it out of the zone more than ever and coming up empty more.  According to Cot’s Baseball Contracts, the Blue Jays have about million on the books for next season, not including Yamaguchi. That is down from 5 million this past season. Toronto has lots of payroll space remaining and could still make a run at Ryu, at least in theory. They also need a first baseman and bullpen help.

  1. RHP Tanner Roark
  2. RHP Chase Anderson
  3. RHP Matt Shoemaker
  4. RHP Shun Yamaguchi
  5. RHP Trent Thornton
  6. LHP Anthony Kay
  7. LHP Ryan Borucki
  8. RHP Jacob Waguespack

With Roark and now Yamaguchi now on board, the Blue Jays’ rotation depth chart currently looks something like this:

On Tuesday, Toronto agreed to a contract with Japanese right-hander Shun Yamaguchi, reports Sportsnet’s Shi Davidi. It’s a two-year deal worth million, according to The Athletic’s Ken Rosenthal. The Blue Jays also owe the Yomiuri Giants, Yamaguchi’s former team in Japan, a .2 million release fee (20 percent of million).