These are players that do not fully fit the definition of starting pitcher or relief pitcher. They are role players: starting, closing, and generally doing whatever is asked of them.
Alfredo Aceves was one of those rare players that actually went from the Yankees to the Red Sox and improved. He had been a big part of the Yankees pitching staff in the World Championship season of 2009 but he was injured frequently in 2010. He was non-tendered by the Yankees in the winter and the Red Sox picked him up off the scrap heap prior to Spring Training.
Not much was expected of Aceves in 2011, but he ended up being a huge part of the Red Sox staff. He was incredibly versatile, starting four games, finishing 15 (two saves), and pitching in middle relief in 36. He was not overpowering, but he had decent control, finishing with a 1.105 WHIP and 42 walks in 114 innings pitched. He struck out 80. The impressive numbers were his 10-2 record and his 2.61 ERA.
2011 was easily Aceves's best season with the Red Sox, and likely the best season of his career. The next season, he became the Red Sox's closer due to the injuries and ineffectiveness of Andrew Bailey and Mark Melancon. His record flipped to 2-10 and his ERA skyrocketed to 5.36, but he saved 25 games. He pitched in just 11 games with the Red Sox in 2013 and had a 4-1 record. He was 16-13 with a 3.94 ERA and 179 strikeouts during his tenure in Boston.
Joe Hesketh (1991): 12-4, league-leading .750 winning percentage, 3.29 ERA
Rolando Arrojo (2001): 3.48 ERA
Tim Wakefield (2002): 11-5, 2.81 ERA, 134 strikeouts
Franklin Morales (2012): 3.77 ERA, 76 strikeouts in 76.1 innings
Steven Wright (2018): 2.68 ERA
What I have been listening to: