KANSAS CITY, Mo. — There was an at-bat in late June that showed everyone with the Chicago Cubs just how much Pete Crow-Armstrong had matured as a hitter. Late in a tie game against the San Diego Padres, lefty Adrian Morejon, one of the best relievers in the game, came in to face the Cubs’ leadoff man.Crow-Armstrong worked a seven-pitch walk, at one point challenging a called strike three he rightfully felt was below the zone. Over the last few weeks, unprompted, manager Craig Counsell and team president Jed Hoyer have brought up that plate appearance to discuss Crow-Armstrong’s improvement against left-handed pitching.“I thought his at-bat against Morejon was the best at-bat I’ve ever seen him take,” Hoyer said recently. “He battled one of the best lefties in the game and laid off a chase slider to walk. We all watched him not do that a lot of times in that situation.”As a whole, no matter who is on the mound, Crow-Armstrong has improved his pitch recognition. It’s been especially impressive against lefties. Coming into the year, Crow-Armstrong had a 60 wRC+ against lefties. Last year, that number was 59, the sixth-worst in baseball among eligible players. This season, he’s dominated southpaws, posting a 165 wRC+, the 10th-best mark in the league.Why the Red Sox resurgence is historicKen Rosenthal and Johnny Sweet“It has completely flipped,” Counsell said. “It’s just different now.”But even this season, it’s been a process. Though his performance in April and May against lefties was strong (114 wRC+), it’s taken off since. In June, he posted a walk rate of 18.9 percent against southpaws; in July, that number soared to 26.7 percent. Overall, his wRC+ against lefties from June 1 on is a robust 217.