Mills met with his pitching coaches before Sunday's game to discuss the club's recent pitching woes. Astros pitchers walked 14 batters in the first two games of the series against the D-backs.
"We'll see what is going through (pitchers') mind at the time and what exactly is their throwing program and how that can be adjusted," Mill said.
At 21 years and 277 days old, Sunday's starter Jordan Lyles is the youngest starting pitcher in the National League. The Astros have the second-youngest active Major League roster in the National League, with an average age of 27.2. The Washington Nationals are the youngest with an average age of 27.1.
Triple-A Oklahoma City's Jimmy Paredes is hitting .531 during his current seven-game hitting streak and has three home runs and eight RBIs during that stretch.
Outfielder Brandon Barnes is riding a nine-game hitting streak, hitting .475 during that span, and fellow outfielder Fernando Martinez has also hit safely in his last nine games, hitting .378 during that stretch for the first-place RedHawks.
The Astros will honor longtime fans Loraine Glenewinkel and Viola Meier Merz during a special pregame ceremony prior to Monday's game. The twin sisters celebrated their 90th birthday last Thursday.