37. Tanner Roark

Every memorable pitching staff features its high-priced aces and highly touted prospects. However, a sustained championship run relies on underrated, gritty workhorses. In Washington, Tanner Roark exemplified that quiet dependability. Traded in 2010 from the Texas Rangers for Cristian Guzman, the right-hander was known for his heavy sinker, sharp slider, and no-nonsense attitude, earning him the nickname "The Diesel." Though often overshadowed by stars like Max Scherzer and Stephen Strasburg, Roark reliably took on vital innings to anchor the Nationals' rotation during their most successful period.

His rise in Washington exemplifies a strategic opportunity turn. After a strong bullpen debut in late 2013, Roark secured a rotation spot in 2014 and experienced an outstanding breakout year. He dominated National League hitters, finishing 15–10 with an impressive 2.85 ERA and a tiny 1.092 WHIP, ranking eighth in the league. When the Nationals added Max Scherzer the next winter, Roark was willingly moved back to the bullpen for much of 2015 to make room for the star-studded rotation. Instead of complaining, he stayed prepared, adapting to different roles and eventually regaining his spot as a starter.

The 2016 campaign marked Roark's finest individual achievement in the Nation’s Capital. Returning to the rotation full-time, he pitched with intense focus and high leverage, setting a career high with 16 wins and logging 210 innings during the regular season. His excellent performance resulted in a 2.83 ERA, earning him tenth place in the National League Cy Young Award voting and confirming his status as a top-tier, front-of-the-rotation starter.

Although his efficiency slightly declined in his last two summers in the District—leading to higher walk rates and more hits allowed—his competitive spirit never faltered. He consistently proved to be a durable, ball-distributing player who often kept Washington in the game. After the 2018 season, as the franchise shifted to a new pitching strategy, the Nationals traded the veteran right-hander to the Cincinnati Reds for Tanner Rainey.

With the Nationals, Roark appeared in 182 games (141 starts), posting a 64–54 record, 3.59 ERA, and 1.20 WHIP. He pitched 930.1 innings, struck out 732, and had a 114 ERA+.