I was listening to Kevin Goldstein's and Jason Parks' podcast (episode 84: This Show is a Disaster). They discuss how there was a Major League team that saw Tim Lincecum as a relief ace in the mold of Goose Gossage. That is, a relief pitcher who could rack up a 150 IP. It requires a pitcher who is capable of bouncing back rather quickly between outings. A player with a rubber arm. There has not truly been a player fitting this mold in 25 years with Toronto's Mark Eichorn. Eichhorn threw 157 IP, but they were high leverage innings and he managed a 6.4 WAR. Before him, the seventies and eighties had several relief aces like the aforementioned Goose Gossage, but also Mike Marshall and Bob Stanley.
I think what ended the era of the relief ace was free agency. Teams used to be more willing to be aggressive with their pitchers. There were no rigid pitch counts and pitchers would throw several bullpen sessions working on pitches. Some pitchers were able were able handle this workload. Others could not. With the increasing cost of free agent pitchers and pitching prospects, it made financial sense to be more protective of prospects. However, because the teams could not figure out who had a rubber arm and who did not, approaches were developed to be protective of all pitchers. The end effect is that the rubber arm pitchers do not have the opportunity to emerge.
Men's Health. Between starts, Dice-K would throw three 150 pitch sessions. He would rarely lift weights, but would do a great deal of cardio and sprints. Some of Dice-K's more amazing feats include a 249 pitch, 17 inning effort and his four day, 38 IP, and 500 pitch effort in a high school tournament. Michael Street also wrote a couple of excellent articles on how pitching is regarded in Japan and mentioned how pitchers are often taught to go deep into pitch counts.
The result is that there are starting pitchers that become available as international free agents usually around the ages of 30-35. Wei-Yin Chen, 26, signed on with the Orioles for roughly 12MM spread over three years. I am unaware of his throwing regimen, but will assume it is similar to the majority of NPB pitchers. For a mid or upper tier revenue team, this cost would be fine to try a solid pitcher with a training background similar to many who have gone throw the NPB system. Chen could be used for high leverage situations every other day and pull in 30-50 pitches in the bullpen and another 30-50 pitches in the game. The Orioles could target Chen for meaningful innings in close games, maximize his performance by having him throw threw the lineup once, and slide him in where his left-handedness may provide him a better opportunity to be successful.
This will not happen though. Chen is slated as a starter. Although I have thought differently, it appears Tsuyoshi Wada does not have a handshake agreement to start. His 86 mph fastball and his fringe breaking balls and change up may have the opportunity to provide a great deal of innings. His marginal offerings suggest that he would not fit the mold of relief ace. Wada could serve as an inning eater in games that have gotten away from the team which would save them from having to use Jim Johnson, Matt Lindstrom, and others in games that are unlikely to matter.