Gray didn't give up a single walk while allowing just one hit while striking out 11 - a season high.
The Cardinals take the first of a three-game series after their 5-0 win.
This is now the sixth shutout on the season for Gray, who has now improved to 8-2 on the year while dropping his earned run average to 3.36.
His 11-strikeout performance now puts the three-time All-Star at 101 on the year, making it his fifth straight season reaching the 100-K mark.
The Cardinals improve to 45-38 on the year and remain in third place in the National League Central Division.
For those new to baseball, throwing a 'Maddux' is when a starting pitcher has a complete game shutout while throwing less than 100 pitches.