John Denny, 1983
John Denny wasn't exactly a "nobody" by the time he came to the Phillies. The soon-to-be 30-year-old righthander had already put up a trio of double-digit win seasons in his career so far, which had been split between St. Louis and Cleveland. After being traded to the Phillies in 1982, he made four starts down the home stretch, effectively auditioning for a starting slot in 1983. The Phillies liked what they saw, so they rolled with him to start the following year. And they're quite glad they did.
After a middling first two starts to open the season, Denny rattled off three complete games to close out the month of April. He followed that up with an excellent May, bringing his ERA all the way down to 1.86 by the end of the month. He continued to put up fine performances every time out (often on just three days rest, mind you), although he somehow was passed over for an All-Star selection.
No matter, though, as Denny kept on chugging along and ended up throwing 242 2/3 innings, putting up a record of 19-6 with a 2.37 ERA to claim one of the most unheralded Cy Young wins in baseball history. He makes an excellent Immaculate Grid answer, as a result.
But, true to form for this list, Denny never recaptured his 1983 magic. He went 7-7 in 1984 (still with a fine ERA), but the cracks really started to show in 1985 when he put up an 11-14 mark and saw his ERA jump by well over a full run. It didn't help that the team around him was getting older and worse, but Denny was nevertheless shipped out to the Reds after the 1985 season. He took a regular turn in their rotation for one season, then hung up his spikes at age 33.