Hamburg defender Kyriakos Papadopoulos faces disciplinary action after criticising interim coach Christian Titz after he was dropped for the 2-1 defeat to Hertha Berlin on Saturday.
Papadopoulos, 26, was only named on the bench while €9.2 million signing Walace, winger Andre Hahn and full-back Denis Diekmeier were left out completely.
Hamburg, the only team to compete in every season of the Bundesliga, then slumped to the foot of the table after Cologne beat Bayer Leverkusen on Sunday.
Last week, academy coach Titz replaced Bernd Hollerbach in the dug out but his wholesale changes failed to bring about an upturn in fortunes and, with only seven matches left, they sit seven points adrift of the relegation playoff place.
"He didn't even talk to the me," said Papadopoulos, who was an unused substitute. "It's just very sad that some very experienced players didn't even make the squad, they are important for the team. This was not the best solution."
Speaking on Sunday, Hamburg interim CEO Frank Wettstein said action would be taken.
"I don't think he has the right to ignore that he made mistakes on the pitch," he said. "We won't tolerate such comments. Who is unreasonable, must take sanctions. When we've spoken to him, we will announce what we'll do."
Papadopoulos is now away with Greece, and will have to face the consequences once he returns to Germany.
Brazil midfielder Walace did not even attend the match, and instead used social media to post pictures from his home. He is also facing action from the club.
"We won't accept this behaviour," Titz said.
He added: "I always try to talk to go through my decisions with all of the players. Sure, the lads can be disappointed. It would be wrong if a player would not like to play. But they should keep the respect, and we need to address that.
"The atmosphere is not really amazing, but we have to look at the many things we did well. We made it clear that we want to build on that. The result is indeed a bit annoying. "
Hamburg also announced that they would ramp up security for their final three home games of the season, after a group of supporters reportedly tried to force their way through to the dressing room following the defeat to Hertha.
While police stopped them, nine people were reportedly injured.
"We don't want those people here," Wettstein said. "This does not leave the players cold. We'll talk to them about what that does to them."
"We will tighten security for our last games."