Mattingly said he sensed Puig's frustration level has, at times, taken him out of his game.
The concern is that Puig's relentless style makes it difficult for him to stay consistent throughout a major league season. Last year, Puig came up in June and sparked the Dodgers' charge until batting .202 in September and having inconsistent at-bats in the playoffs.
"The season is long, and it wears you down," Mattingly said. "It's part of learning to regulate yourself here, as far as rest or anything else. We've seen Dee Gordon and how much more consistent his approach is day in and day out now, staying at a certain level. I think Yasiel's really emotional, and it's hard to be really emotional and play 162."
Puig did pinch hit for pitcher Dan Haren in the seventh inning of Friday night's 3-2 loss to the Padres and struck out against Nick Vincent to end the inning.
Entering Friday, Puig was batting .192 in his previous 20 games. He was invited to participate in the Home Run Derby at the All-Star Game, yet he has hit just two home runs since May 28. Mattingly said Puig is showing signs of frustration, often swinging at pitches well outside the strike zone.
Puig, who has played in 123 of the Dodgers' 135 games, was the player of the month in May, when he batted .398 with 25 RBIs. In June, he batted .248 with five RBIs. He led the majors in slugging percentage (.688) in July but has just two extra-base hits in August. Overall, he ranks 10th in the National League in batting average (.300) and sixth in OPS (.881).
There have been times when Puig's work ethic has been an issue for the team, but Mattingly said he doesn't sense that is the problem now. More than once this season, Puig has shown up late for stretching and has been fined. He does not study video.
Mattingly compared Puig's style of preparation to that of two Hall of Famers he played with, Rickey Henderson and Dave Winfield.
"I've seen it both ways. I've seen guys who are consistently here early doing early work all the time. I've also seen some guys that are in the Hall of Fame that got to the park late, got themselves ready to play and go, and do that every day," Mattingly said. "I don't think there's one way to do it."
Even with Puig slumping, the Dodgers have won six of their past nine games while averaging nearly five runs per game.
"Obviously, we're going to be better if he's rolling. We can't deny that," Mattingly said. "Obviously, we'd like to get him back to the form he had in the first half. That's going to make us better and a little more dynamic."
Information from The Associated Press was used in this report.