But Wainwright had to push those thoughts aside as he pitched seven strong innings to lead the Cardinals to a 10-2 win over Milwaukee for a tie atop the NL Central.
The Brewers lost their seventh in a row.
Segura left the team and traveled home to the Dominican Republic, a day after his 9-month-old son died. The Brewers observed a moment of silence for Janniel Segura, and the clubhouse was closed before the game.
The 24-year-old shortstop was put on the bereavement list when he learned after the Brewers' 7-6 loss to St. Louis on Friday night that his son had died. Manager Ron Roenicke said the boy had been ill.
''When something like that happens, you become a family,'' Wainwright said. ''Baseball as a whole becomes a family. There's bigger things than baseball. I understand that he's going through something that I hope I never, never have to go through. So our hearts and prayers go out to him.''
Cardinals manager Mike Matheny was catcher for the Cardinals when St. Louis pitcher Darryl Kile died of a heart problem on June 22, 2002.
''The extended family in (Milwaukee's) clubhouse is hurting right along with him,'' he said. ''You can't help but take a step back and just prioritize life. Prioritize just how fragile it is. It gives us perspective.''
''When that happened (Kile's death), we had a lot of guys having a bunch of conversations you typically wouldn't have inside a clubhouse,'' Matheny said.
Wainwright (12-4) gave up two runs and five hits. He has allowed just four earned runs in his last six starts.
St. Louis trailed Milwaukee by 6 1/2 games on July 1, but Wainwright knows how quickly a team's fortune can change in a week. In fact, he said that a week ago.
''My quote was `In a week from now, we could be doing a completely different kind of interview,''' he said. ''It could be what has turned the season around for. And, that's what's happened. This game is a funny game of ups and downs. The teams that have the most ups and the least amount of downs end up winning the whole thing.''
''It's nice to be able to make a little ground,'' Matheny said. ''It just comes back to playing each game the right way.''
For the Brewers, it was a most difficult day.
''I think everybody in the clubhouse was affected quite a bit,'' manager Ron Roenicke said. ''I don't want to make excuses. We knew that we still have a game to play and a job to do, but we did not play well today.''
The Brewers have lost 11 of 12. They had held sole possession of first place since April 9.
Frustrated Brewers star Carlos Gomez struck out swinging in the fifth inning and tried three times without success to break the bat over his leg. He slammed his helmet and tore up his batting gloves.
Jimmy Nelson (1-1) went 4 1/3 innings, giving up eight runs and eight hits. He was recalled from Triple-A Nashville on Thursday to make his first start since replacing ineffective Marco Estrada in the rotation.
St. Louis took a 3-0 lead in the first inning. A two-out error by second baseman Scooter Gennett on a grounder set up Cruz's two-run single.
Wong hit a two-run homer in the second. It was his fifth home run in the last six games since coming back from the disabled list.
Cruz doubled home a run in the third.
NOTES: Milwaukee recalled INF Elian Herrera from Triple-A Nashville to replace Segura on the roster. ... The Brewers will start RHP Wily Peralta (9-6) in the series finale Sunday against Carlos Martinez (2-3).