Wednesday head coach Carvalhal said the defender met a specialist to discuss the injury last week.
And The Star can exclusively reveal that Lees has since gone under the knife after discovering the full extent of the problem and is expected to be out for six to eight weeks.
The 26-year-old tried to play through the pain barrier for a long period. He initially felt pain in his adductor muscle after Wednesday’s home victory over Millwall at the end of October.
“He started feeling the pain in the Millwall game,” admitted Carvalhal. “It was in this period in the last two seasons where he had a very hard injury.”
As Carvalhal alluded to, it is the third year running Lees has been hampered by injury problems. A hamstring knock kept Lees out of action for a big chunk of the 2015/16 campaign and he was troubled by knee issue last year.
Lees’ injury setback leaves the Owls with just three senior centre-halves: Glenn Loovens, Joost van Aken and Frederico Venancio. It is a big blow for Carvalhal, who was sent to the stands in Saturday’s disappointing 2-2 draw with lowly Hull City. The Portuguese chief was left fuming after referee Mike Jones denied Wednesday a late penalty at Hillsborough.
Carvalhal claimed Tigers defender Michael Dawson handled Adam Reach’s goalbound effort in the 82nd minute. Jones waved play on and later dismissed Carvalhal for his appeals.
To compound Carvalhal’s woes, Dawson equalised deep into added on time to sentence the Owls to a fourth consecutive draw.
Carvalhal focused his post-match anger on Jones, describing it as an “unbelievable decision” in a 12-minute rant.
“You will see it on TV, it is easy to understand,” he said. “It is a clear penalty, my natural reaction was to hold my hands out and go out of my technical area.
“I believe 90 per cent of coaches, if they are not injured, will do the same. It’s natural, you have a reaction. I was maybe three, four metres maximum, outside and I went back. I said ‘communicate with the referee, you saw it’, he said ‘no, you are out’.”
He feels refereeing decisions have cost his team 10 points this season.
“With them (points) I would be in a different position,” said Carvalhal. “This is the reality.
“If things change, we can fight for something. If things don’t change, it will be very difficult to us. If they don’t see penalties, red cards, and decisions like that against us, it will be impossible. If things are normal, we still believe.”
Carvalhal could be in trouble with the Football Association following his second dismissal of the season and his third in 2017.
He was handed a two-match touchline ban and fined £4,000 after his altercation with Bolton Wanderers counterpart Phil Parkinson in the Carabao Cup last August. Carvalhal was sent to the stands and then engaged in a heated discussion with a steward as he attempted to take a seat behind the dug-out. He was not in the technical area for their home wins over Nottingham Forest and Brentford.
As for Wednesday, the Hull draw stretched their unbeaten run to seven matches but saw them fall a place to 12th in the rankings.