Since then the Astros haven't had error and have been taking advantage of their opponents' miscues.
Travis Buck drove in two runs, Justin Maxwell homered in his Houston debut and the Astros rebounded from an early deficit thanks to sloppy defensive play by the Atlanta Braves in an 8-3 win on Monday night.
"We talked about Opening Day and us giving the Rockies extra outs," Mills said. "It's nice to see us (not make errors)."
The loss drops Atlanta to 0-4 for the first time since losing 10 straight to open the 1988 season. The Astros are 3-1 after finishing last season with baseball's worst record.
Houston trailed 3-0 in the third before a trio of errors by the Braves, with two from third baseman Juan Francisco, led to three unearned runs and tied the game.
"It's great to see our guys realize they can come back," Mills said. "We were able to string some hits together and score some runs. What a confidence booster for this game to be able to get back into like that."
Astros starter J.A. Happ drove in the go-ahead run with an RBI single in the fourth inning that made it 4-3. Pinch-hitter J.D. Martinez and Jose Altuve drove in a run each in the sixth to stretch the lead to 6-3.
After starting 0-5 last season and losing eight in a row to start the 2010 season, the Astros are pretty excited about their start, which is their best since 2006.
"We'd like to keep going and build off of it and try to build some momentum if we can," Happ said.
Happ (1-0) allowed six hits and three runs with five strikeouts in six innings for the win.
Braves starter Brandon Beachy (0-1) allowed four hits and four runs -- one earned -- in five innings.
Maxwell, acquired from the Yankees on Sunday, hit a two-run homer as a pinch hitter in the eighth inning. He didn't have much time to get acquainted with his new team after arriving Monday afternoon. He said the hardest part was learning everyone's name, but not all the Astros got his right.
"Somebody called me Jason, but I'll forgive them," he said with a laugh.
Francisco, who the Braves acquired from Cincinnati on April 1, had three of Atlanta's errors starting in place of Chipper Jones, who is on the disabled list.
"That's not me. I don't throw like that," Francisco said in Spanish. "The first one I felt got away from me, and the second I threw it down for some reason."
The Astros got four hits and drove in two runs in the sixth inning off Livan Hernandez, who signed with the Braves after he was released by the Astros in spring training.
Rookie Marwin Gonzalez, who had three hits and scored three runs, doubled in the fourth before Happ helped his cause with his run-scoring single to right field that gave Houston a 4-3 lead.
Beachy walked Jordan Schafer with two outs in the third before Altuve reached on a fielding error by Francisco. A second error by Francisco on the same play, this time on the throw to third, allowed Schafer to advance to third.
"I think it was big," Braves manager Fredi Gonzalez said of the errors. "We were playing good baseball up to that point, and all of a sudden we mishandled some of the plays back there, and we weren't real pretty after that as a team."
Buck followed with a two-RBI double to get Houston within 3-2. He reached third on the play after an error by Tyler Pastornicky.
Lee tied it 3-3 with a single to center field which scored Buck. Beachy finally got out of the inning when Brian Bogusevic grounded out.
Happ got on track after McCann's RBI, retiring the next 11 in a row, striking out five. He didn't allow another base runner until Matt Diaz walked with two outs in the sixth, but Francisco lined out to end the inning.
Freddie Freeman singled with one out in the second before Diaz grounded into a force out that left Freeman out at second. The Braves then hit three consecutive singles, with the last two by Pastornicky and Beachy driving in runs, to give Atlanta a 2-0 lead.
The Astros optioned LHP Fernando Abad to Triple-A Oklahoma City on Monday to make room on the roster for Maxwell. ... Former Astros star Craig Biggio helped Houston honor Jones, who said he will retire at the end of this season, before the game. Biggio presented Jones with a cowboy hat as footage of his many memorable games against the Astros played on the video screen. Jones is on the disabled list after surgery March 26 to repair a torn meniscus in his left knee, but expects to be activated on Tuesday.