DeFrancesco addressed the team during a whirlwind Sunday morning in which he met the media and filled out his first lineup card.
"We had a greet meeting," pitcher Bud Norris said. "He definitely re-energized this group, and I'm excited for these last 41 games. We have to go out and play hard and have something more to fight for."
Mills, who was hired prior to the 2010 season, went 171-274 in 445 games as manager, suffering through a 106-loss season a year ago. Players who have been dealing with a flurry of changes on the roster were digesting a change in the managerial chair on Sunday morning.
"It's one of those things with this game and this business that the only certainty is change," veteran catcher Chris Snyder said. "I think a change here will be good. It mixes things up a little bit and gives these guys a fresh start."
DeFrancesco is no stranger to many of the players, having spent the last two seasons at the helm of the Astros' Triple-A affiliate in Oklahoma City. Several players on the 25-man roster have had experience playing for DeFrancesco, including seven who were in the starting lineup Sunday against the D-backs.
"He's going to try to get us going and try to motivate us, and I think the biggest thing he wants to do is win," infielder Brett Wallace said. "Whatever our record is, he's not worried about what we've done in the past. He wants us to go out there and compete."
DeFrancesco, who has a 1,235-1,088 record in the Minor Leagues, spent seven years managing at Triple-A Sacramento in the Oakland system prior to joining the Astros, and has 17 seasons of managerial experience, overall.
"It's definitely exciting when someone gets called up that's been grinding it out at the Minor League level," Wallace said. "You kind of root for him. He's awesome. He's paid his dues, and hopefully he can help us turn this thing around."
Wallace knows DeFrancesco better than anybody, having played 44 games for him in Sacramento in 2009 and 114 combined at Oklahoma City the last two years.
"He's passionate," Wallace said. "He likes to win and he's a motivator. At the end of the day, he's always won and he wants us to get better every day and work hard. He keeps it pretty loose. He's not a real uptight guy. He can joke around with you and have fun, and I think that's the biggest thing."
Wright said the onus is on the players to get better on the field.
"No matter who the manager is, the players have to go out there and make plays," Wright said. "We're the guys on the field, and we're pretty much responsible for the wins and losses, for the most part. It comes down to what we do on the field. The manager can bring what he can, but at the end of the day, it's all about the players."