Roark, 32, has generally struggled over the past two seasons, but he has the potential to be one of baseball’s best starting pitchers when he’s right. He’s had three different seasons with an ERA under 3.00 and a WHIP under 1.20, most notably the 2016 campaign, during which he posted a 2.83 ERA and a 1.17 WHIP over 210 innings for the Nats and finished 10th in NL Cy Young voting. He’s posted an ERA over 4.00 in his remaining three major-league seasons, though, and it’s fair to say that he was slightly below-average in 2018, posting a 4.34 ERA and a 1.28 WHIP with just 146 strikeouts and 50 walks in 180.1 innings.
As he moves to the bandbox that is Cincinnati’s Great American Ball Park, it’ll be interesting to see what kind of adjustments Roark is able to make. He’s been prone to the home run over the past two years, allowing 1.17 homers per nine innings, which is 21st-worst among qualifying pitchers over that period. He certainly adds some much-needed experience to the Reds’ rotation, though; other than Homer Bailey, who is arguably the majors’ worst pitcher at this point and may be moved this offseason, Anthony DeSclafani is the only starter currently on the Reds roster with more than 50 MLB starts.
It seems that the Nationals sold low on Roark, particularly since they don’t have a lot of rotation depth to offset his loss; Erick Fedde and Joe Ross are now projected to occupy the fourth and fifth rotation spots behind the dominant top three of Max Scherzer, Stephen Strasburg, and Patrick Corbin. But with the Nationals desperately needing a new second baseman and possibly needing to add some more established depth in the bullpen and outfield, it’s understandable why they’d be motivated to move Roark, who is a free agent next winter and is projected by MLB Trade Rumors to earn $9.8 million through the arbitration process this offseason.
The 25-year-old Rainey, who has been exclusively a reliever for the past two seasons, had an absolutely disastrous introduction to the big leagues in 2018, posting a 24.43 ERA and a 3.57 WHIP with seven strikeouts and 12 walks over seven innings. He was rather successful in his first season at Triple-A Louisville, though, posting a 2.65 ERA and 1.18 WHIP over 44 appearances (51 innings), so the Nats will be hoping that he can carry that form into a more prominent major-league role at some point in the future.