"There was no intent on the equipment hitting him," Farrell said. "Equipment hits an umpire, it's their immediate prerogative to eject the player. We needed Nap to stay in the game. Unfortunately, the helmet hits him, and he's ejected."
Daniel Nava replaced Napoli at first base, and went 0-for-2 while reaching base on a walk and a hit-by-pitch.
Napoli, a likely candidate to be moved before the non-waiver Trade Deadline, is hitting .208/.305/.376 amid a disappointing season with the Red Sox. However, he has regained his rhythm at the plate in recent days, going 10-for-29 with five extra-base hits in nine games since the All-Star break.
"What's been most encouraging is pitches in the strike zone that he's squaring up, that he's not missing," Farrell said before the game. "He's still taking his walks, but I think he's more confident. He shows more confidence at the plate.
"There's at-bats where he's offering at the first pitch and putting good swings on some pitches that's putting some doubt in a pitcher's mind. Early on, Mike was so take-oriented maybe early in the count to see pitches that he was allowing pitchers to get ahead early and put him in a disadvantaged count."
But in order to contribute, Farrell noted, Napoli has to keep his emotions in check and remain in the game.
"There's always a line of composure that's got to be held, and unfortunately the helmet bounced up and hit [the umpire]," Farrell said.
Alec Shirkey is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.