In a release Wednesday, the NHL said Pronger was suspended for "a blow to the head" of Holmstrom during Game 3 on Tuesday.
The Red Wings go into Thursday's game with a 2-1 lead in the best-of-seven series.
Pronger was unavailable for comment but Ducks general manager Brian Burke disagreed with the league's decision, suggesting part of the problem was that Holmstrom didn't have his helmet done up properly.
"We disagree completely," said Burke. "But we respect the process. These things are not easy."
Pronger and Rob Niedermayer hammered Holmstrom into the boards from behind at 11:40 of the second period of Game 3, a 5-0 Wings win.
Holmstrom, who had two goals and an assist in the victory, had to be helped off the ice. He needed 13 stitches to repair two cuts on his forehead but returned for the third period.
Pronger was not penalized while Niedermayer was given a five-minute boarding penalty and a game misconduct.
Replays appeared to show that Pronger got his elbows up and hit Holmstrom in the head.
Burke said Pronger "was sour" about being suspended.
"Chris Pronger is an elite player in our league," said Burke. "He's a tough Canadian kid that plays the game the way we want to play. We don't approve of guys headhunting. We don't think that's what this was.
"The player had two cuts, both of which would have been covered by his helmet if it had been properly attached. I think it came off four times last night."
Burke argued the taller Pronger wasn't trying to hurt Holmstrom.
"If you watch the replay. . . his arms never go above his shoulders," said Burke. "He's not headhunting there. He's six-foot-six hitting a guy who is six-foot-one. I think the blow was to the shoulders and rode up to the head when the player stopped.
"Did it end up as a head shot? I'd have to concede that but I don't think that's how it started out. I don't think Chris Pronger meant to injure this player."
Ducks coach Randy Carlyle says the team will adjust without Pronger, who has been nominated again for the Norris Trophy as the league's top defenceman.
"He's a big part of our hockey club," said Carlyle. "But we've had stretches through the season where he wasn't on our blue-line."
Pronger missed nine games this season with a broken foot and seven with a broken toe.
"We'll move other people in, making some adjustments without personnel. Other people will have to share those minutes."
Ducks captain Scott Niedermayer was frustrated by the league's action.
"The call last night was five minutes to Rob Niedermayer," he said. "Today they're talking to Chris. Does that make sense to anybody?"