Instead of canning the source of the problem (when the inevitable happens, may as well let him finish out the year) and going into the offseason with a plan to improve, Detroit will probably suffer through more Leylandball next year, fire him in the middle of the season then have to go through the annoyance of an interim manager and candidate search.
Listen: fool me once, shame on you; fool me twice, shame on me. Fool me three times, that's a crowd. Fool me four times, maybe I should start to see a pattern. Fool me five times and I'll give you a contract extension.