But manager Kirk Gibson doesn't care.
"Obviously you want to be there," Gibson said. "But you have to keep that in perspective. It doesn't really mean anything. We want to be there the last day of the season, that's where we want to be.
"I guess as a benchmark of where we want to be, I guess it's good to be there to know where you want to stay."
But Gibson and outfielder Chris Young both said that there wasn't a change in the team's demeanor Thursday.
"It doesn't feel any different than it did yesterday," Young said. "By no means just because you're in first place, the season isn't over yet, we still need to continue to work and we still have a lot more games to win if we want to be in the playoffs."
The D-backs have been a half-game up on the Giants in the National League West 10 times this season but have never led by more than that. They were looking to stand a game up with a victory over the Astros on Thursday, while the Giants are idle.
"We'll approach every game the same, win or lose, then we'll go to the next game," Gibson said. "We have such a long way to go.
"Is it significant? I'm not sure it is right now."