The 23-year-old missed the 36-26 loss to Sydney Roosters on Friday night but Kristian Woolf confirmed post-match the injury was more serious than first thought after Plath left the field in the 42-22 win over Melbourne on Good Friday.
"Max ended up with a minor surgery so he will be out for three or four weeks," Woolf said.
There was better news on prop Feliise Kaufusi (knee) and utility Kurt Donoghoe (calf), who also were unavailable against the Roosters.
Woolf said both were likely to return for Thursday night's away clash with Parramatta.
Plath had been in the frame for a State of Orgin debut for Queensland on May 28 after coach Billy Slater told AAP he was impressed with the versatile utility. Slater said Plath was building habits in his game that were "Origin worthy".
That is why the Dolphins have missed his presence the last two games when they were exposed in the forwards.
"What I was disappointed with the most is I don't think we defended to our standards," Woolf said.
The Dolphins lost their opening three games of the season, won the next three and lost the following two.
"We do need to get rolling again," Woolf said.
"We rolled really well there for three weeks and, for whatever reason, things have changed. We need to figure out why they have changed and what we have got to change."
The Dolphins have started the season 3-6 and can only lose another six games maximum in their next 15 or miss out on finals.
Captain Tom Gilbert was blunt about his team's performance against the Roosters., which followed a 40-28 capitulation to Canberra after the Dolphins led 28-10 at halftime.
"The Roosters came in with a tough mindset. In patches we showed that we do have a tough mindset but we didn't want to do that consistently," he said.
"It is definitely something we need to address and is not something as a captain, or a teammate, that we want to see again this season."
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