Mills and two members of his coaching staff were fired soon after the 12-4 defeat to the Arizona Diamondbacks.
Tony DeFrancesco has been appointed as interim manager of Houston - but he failed to have an immediate impact on their fortunes as an 8-1 defeat gave the Diamondbacks a three-game sweep.
Pedro Alvarez hit the game-winning homer and Andrew McCutchen provided some insurance runs as the Pittsburgh Pirates prevailed in their 19th inning of their marathon clash with the St Louis Blues - it ended 6-3.
The Seattle Mariners beat the Minnesota Twins 5-1 to complete their third second-half sweep, while the San Diego Padres snapped a five-game losing run with a 7-1 success over the San Francisco Giants.
The Oakland Athletics maintained their hopes of extending their season with a fourth successive win - 4-0 over the Cleveland Indians, while a four run second inning put the Tampa Bay Rays on the way to an 8-3 victory over the LA Angels.
Kyle Kendrick produced eight scoreless frames in Milwaukee, allowing just three hits and tying a career high with seven strikeouts, as the Philadelphia Phillies downed the Brewers 8-0.
The Atlanta Braves were also blanked, 5-0 by the LA Dodgers, while the injury-hit Colorado Rockies overcame the Miami Marlins 3-2,
The Kansas City Royals scored a fifth win in six games, 5-2 against the Chicago White Sox, to complete a sweep of the AL Central leaders.
The Baltimore Orioles saw off the Detroit Tigers 7-5, while the Washington Nationals sunk the New York Mets 5-2 in a contest which was delayed for two and a half hours by rain.
Elsewhere, the Texas Rangers defeated the Toronto Blue Jays 11-2, the Cincinnati Reds beat the Chicago Cubs 5-4 and the New York Yankees won 4-1 against the Boston Red Sox.