I thought this was going to include Jim Riggleman who is filling in on the Reds since their Manager was fired after what 20+ games with only 3 wins. A Few years back for the Nationals he interimed and eventually replaced Manny Acta.

@captkirk42 It is. I haven't gotten to him yet.

Oh the old 1980 Cardinals, with 4 managers in the span of about two months.  Then the season ended and Whitey got the job again.

and the 1990 Cardinals, the team's only last place finish since 1918.  They had 3 managers that year. Whitey, Red, and Joe Torre, all in the hall of fame now.

This is nitpicking, but MLB will tell you that the season really begins in the grapefruit and cactus leagues.  I remember when Alvin Dark got canned by San Diego during spring training in 1978 ... after further research, March 21 to be exact.  The only other skipper to be let go during the spring before Dark was the Cubs' Phil Cavaretta in 1954 ... per Wikipedia, it happened after he admitted that the team was unlikely to finish above 5th place (they finished 7th).

John Schneider for the Blue Jays

Roy McMillan managed two games (1-1) for the '72 Brewers, in between the firing of Dave Bristol and hiring and Del Crandall.